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# `importlib` --- The implementation of `import`
3\.1 新版功能.
**Source code:** [Lib/importlib/\_\_init\_\_.py](https://github.com/python/cpython/tree/3.7/Lib/importlib/__init__.py) \[https://github.com/python/cpython/tree/3.7/Lib/importlib/\_\_init\_\_.py\]
- - - - - -
## 概述
The purpose of the [`importlib`](#module-importlib "importlib: The implementation of the import machinery.") package is two-fold. One is to provide the implementation of the [`import`](../reference/simple_stmts.xhtml#import) statement (and thus, by extension, the [`__import__()`](functions.xhtml#__import__ "__import__") function) in Python source code. This provides an implementation of `import` which is portable to any Python interpreter. This also provides an implementation which is easier to comprehend than one implemented in a programming language other than Python.
Two, the components to implement [`import`](../reference/simple_stmts.xhtml#import) are exposed in this package, making it easier for users to create their own custom objects (known generically as an [importer](../glossary.xhtml#term-importer)) to participate in the import process.
参见
[import 语句](../reference/simple_stmts.xhtml#import)The language reference for the [`import`](../reference/simple_stmts.xhtml#import) statement.
[Packages specification](https://www.python.org/doc/essays/packages/) \[https://www.python.org/doc/essays/packages/\]Original specification of packages. Some semantics have changed since the writing of this document (e.g. redirecting based on `None`in [`sys.modules`](sys.xhtml#sys.modules "sys.modules")).
The [`__import__()`](#importlib.__import__ "importlib.__import__") functionThe [`import`](../reference/simple_stmts.xhtml#import) statement is syntactic sugar for this function.
[**PEP 235**](https://www.python.org/dev/peps/pep-0235) \[https://www.python.org/dev/peps/pep-0235\]Import on Case-Insensitive Platforms
[**PEP 263**](https://www.python.org/dev/peps/pep-0263) \[https://www.python.org/dev/peps/pep-0263\]Defining Python Source Code Encodings
[**PEP 302**](https://www.python.org/dev/peps/pep-0302) \[https://www.python.org/dev/peps/pep-0302\]New Import Hooks
[**PEP 328**](https://www.python.org/dev/peps/pep-0328) \[https://www.python.org/dev/peps/pep-0328\]Imports: Multi-Line and Absolute/Relative
[**PEP 366**](https://www.python.org/dev/peps/pep-0366) \[https://www.python.org/dev/peps/pep-0366\]Main module explicit relative imports
[**PEP 420**](https://www.python.org/dev/peps/pep-0420) \[https://www.python.org/dev/peps/pep-0420\]Implicit namespace packages
[**PEP 451**](https://www.python.org/dev/peps/pep-0451) \[https://www.python.org/dev/peps/pep-0451\]A ModuleSpec Type for the Import System
[**PEP 488**](https://www.python.org/dev/peps/pep-0488) \[https://www.python.org/dev/peps/pep-0488\]Elimination of PYO files
[**PEP 489**](https://www.python.org/dev/peps/pep-0489) \[https://www.python.org/dev/peps/pep-0489\]Multi-phase extension module initialization
[**PEP 552**](https://www.python.org/dev/peps/pep-0552) \[https://www.python.org/dev/peps/pep-0552\]Deterministic pycs
[**PEP 3120**](https://www.python.org/dev/peps/pep-3120) \[https://www.python.org/dev/peps/pep-3120\]Using UTF-8 as the Default Source Encoding
[**PEP 3147**](https://www.python.org/dev/peps/pep-3147) \[https://www.python.org/dev/peps/pep-3147\]PYC Repository Directories
## 函数
`importlib.``__import__`(*name*, *globals=None*, *locals=None*, *fromlist=()*, *level=0*)An implementation of the built-in [`__import__()`](functions.xhtml#__import__ "__import__") function.
注解
Programmatic importing of modules should use [`import_module()`](#importlib.import_module "importlib.import_module")instead of this function.
`importlib.``import_module`(*name*, *package=None*)Import a module. The *name* argument specifies what module to import in absolute or relative terms (e.g. either `pkg.mod` or `..mod`). If the name is specified in relative terms, then the *package* argument must be set to the name of the package which is to act as the anchor for resolving the package name (e.g. `import_module('..mod', 'pkg.subpkg')` will import `pkg.mod`).
The [`import_module()`](#importlib.import_module "importlib.import_module") function acts as a simplifying wrapper around [`importlib.__import__()`](#importlib.__import__ "importlib.__import__"). This means all semantics of the function are derived from [`importlib.__import__()`](#importlib.__import__ "importlib.__import__"). The most important difference between these two functions is that [`import_module()`](#importlib.import_module "importlib.import_module") returns the specified package or module (e.g. `pkg.mod`), while [`__import__()`](functions.xhtml#__import__ "__import__")returns the top-level package or module (e.g. `pkg`).
If you are dynamically importing a module that was created since the interpreter began execution (e.g., created a Python source file), you may need to call [`invalidate_caches()`](#importlib.invalidate_caches "importlib.invalidate_caches") in order for the new module to be noticed by the import system.
在 3.3 版更改: Parent packages are automatically imported.
`importlib.``find_loader`(*name*, *path=None*)Find the loader for a module, optionally within the specified *path*. If the module is in [`sys.modules`](sys.xhtml#sys.modules "sys.modules"), then `sys.modules[name].__loader__` is returned (unless the loader would be `None` or is not set, in which case [`ValueError`](exceptions.xhtml#ValueError "ValueError") is raised). Otherwise a search using [`sys.meta_path`](sys.xhtml#sys.meta_path "sys.meta_path")is done. `None` is returned if no loader is found.
A dotted name does not have its parents implicitly imported as that requires loading them and that may not be desired. To properly import a submodule you will need to import all parent packages of the submodule and use the correct argument to *path*.
3\.3 新版功能.
在 3.4 版更改: If `__loader__` is not set, raise [`ValueError`](exceptions.xhtml#ValueError "ValueError"), just like when the attribute is set to `None`.
3\.4 版后已移除: Use [`importlib.util.find_spec()`](#importlib.util.find_spec "importlib.util.find_spec") instead.
`importlib.``invalidate_caches`()Invalidate the internal caches of finders stored at [`sys.meta_path`](sys.xhtml#sys.meta_path "sys.meta_path"). If a finder implements `invalidate_caches()` then it will be called to perform the invalidation. This function should be called if any modules are created/installed while your program is running to guarantee all finders will notice the new module's existence.
3\.3 新版功能.
`importlib.``reload`(*module*)Reload a previously imported *module*. The argument must be a module object, so it must have been successfully imported before. This is useful if you have edited the module source file using an external editor and want to try out the new version without leaving the Python interpreter. The return value is the module object (which can be different if re-importing causes a different object to be placed in [`sys.modules`](sys.xhtml#sys.modules "sys.modules")).
When [`reload()`](#importlib.reload "importlib.reload") is executed:
- Python module's code is recompiled and the module-level code re-executed, defining a new set of objects which are bound to names in the module's dictionary by reusing the [loader](../glossary.xhtml#term-loader) which originally loaded the module. The `init` function of extension modules is not called a second time.
- As with all other objects in Python the old objects are only reclaimed after their reference counts drop to zero.
- The names in the module namespace are updated to point to any new or changed objects.
- Other references to the old objects (such as names external to the module) are not rebound to refer to the new objects and must be updated in each namespace where they occur if that is desired.
There are a number of other caveats:
When a module is reloaded, its dictionary (containing the module's global variables) is retained. Redefinitions of names will override the old definitions, so this is generally not a problem. If the new version of a module does not define a name that was defined by the old version, the old definition remains. This feature can be used to the module's advantage if it maintains a global table or cache of objects --- with a [`try`](../reference/compound_stmts.xhtml#try)statement it can test for the table's presence and skip its initialization if desired:
```
try:
cache
except NameError:
cache = {}
```
It is generally not very useful to reload built-in or dynamically loaded modules. Reloading [`sys`](sys.xhtml#module-sys "sys: Access system-specific parameters and functions."), [`__main__`](__main__.xhtml#module-__main__ "__main__: The environment where the top-level script is run."), [`builtins`](builtins.xhtml#module-builtins "builtins: The module that provides the built-in namespace.") and other key modules is not recommended. In many cases extension modules are not designed to be initialized more than once, and may fail in arbitrary ways when reloaded.
If a module imports objects from another module using [`from`](../reference/simple_stmts.xhtml#from) ... [`import`](../reference/simple_stmts.xhtml#import) ..., calling [`reload()`](#importlib.reload "importlib.reload") for the other module does not redefine the objects imported from it --- one way around this is to re-execute the `from` statement, another is to use `import`and qualified names (*module.name*) instead.
If a module instantiates instances of a class, reloading the module that defines the class does not affect the method definitions of the instances --- they continue to use the old class definition. The same is true for derived classes.
3\.4 新版功能.
在 3.7 版更改: [`ModuleNotFoundError`](exceptions.xhtml#ModuleNotFoundError "ModuleNotFoundError") is raised when the module being reloaded lacks a `ModuleSpec`.
## [`importlib.abc`](#module-importlib.abc "importlib.abc: Abstract base classes related to import") -- Abstract base classes related to import
**Source code:** [Lib/importlib/abc.py](https://github.com/python/cpython/tree/3.7/Lib/importlib/abc.py) \[https://github.com/python/cpython/tree/3.7/Lib/importlib/abc.py\]
- - - - - -
The [`importlib.abc`](#module-importlib.abc "importlib.abc: Abstract base classes related to import") module contains all of the core abstract base classes used by [`import`](../reference/simple_stmts.xhtml#import). Some subclasses of the core abstract base classes are also provided to help in implementing the core ABCs.
ABC hierarchy:
```
object
+-- Finder (deprecated)
| +-- MetaPathFinder
| +-- PathEntryFinder
+-- Loader
+-- ResourceLoader --------+
+-- InspectLoader |
+-- ExecutionLoader --+
+-- FileLoader
+-- SourceLoader
```
*class* `importlib.abc.``Finder`An abstract base class representing a [finder](../glossary.xhtml#term-finder).
3\.3 版后已移除: Use [`MetaPathFinder`](#importlib.abc.MetaPathFinder "importlib.abc.MetaPathFinder") or [`PathEntryFinder`](#importlib.abc.PathEntryFinder "importlib.abc.PathEntryFinder") instead.
*abstractmethod* `find_module`(*fullname*, *path=None*)An abstract method for finding a [loader](../glossary.xhtml#term-loader) for the specified module. Originally specified in [**PEP 302**](https://www.python.org/dev/peps/pep-0302) \[https://www.python.org/dev/peps/pep-0302\], this method was meant for use in [`sys.meta_path`](sys.xhtml#sys.meta_path "sys.meta_path") and in the path-based import subsystem.
在 3.4 版更改: Returns `None` when called instead of raising [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError").
*class* `importlib.abc.``MetaPathFinder`An abstract base class representing a [meta path finder](../glossary.xhtml#term-meta-path-finder). For compatibility, this is a subclass of [`Finder`](#importlib.abc.Finder "importlib.abc.Finder").
3\.3 新版功能.
`find_spec`(*fullname*, *path*, *target=None*)An abstract method for finding a [spec](../glossary.xhtml#term-module-spec) for the specified module. If this is a top-level import, *path* will be `None`. Otherwise, this is a search for a subpackage or module and *path* will be the value of [`__path__`](../reference/import.xhtml#__path__ "__path__") from the parent package. If a spec cannot be found, `None` is returned. When passed in, `target` is a module object that the finder may use to make a more educated guess about what spec to return.
3\.4 新版功能.
`find_module`(*fullname*, *path*)A legacy method for finding a [loader](../glossary.xhtml#term-loader) for the specified module. If this is a top-level import, *path* will be `None`. Otherwise, this is a search for a subpackage or module and *path*will be the value of [`__path__`](../reference/import.xhtml#__path__ "__path__") from the parent package. If a loader cannot be found, `None` is returned.
If [`find_spec()`](#importlib.abc.MetaPathFinder.find_spec "importlib.abc.MetaPathFinder.find_spec") is defined, backwards-compatible functionality is provided.
在 3.4 版更改: Returns `None` when called instead of raising [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError"). Can use [`find_spec()`](#importlib.abc.MetaPathFinder.find_spec "importlib.abc.MetaPathFinder.find_spec") to provide functionality.
3\.4 版后已移除: Use [`find_spec()`](#importlib.abc.MetaPathFinder.find_spec "importlib.abc.MetaPathFinder.find_spec") instead.
`invalidate_caches`()An optional method which, when called, should invalidate any internal cache used by the finder. Used by [`importlib.invalidate_caches()`](#importlib.invalidate_caches "importlib.invalidate_caches")when invalidating the caches of all finders on [`sys.meta_path`](sys.xhtml#sys.meta_path "sys.meta_path").
在 3.4 版更改: Returns `None` when called instead of `NotImplemented`.
*class* `importlib.abc.``PathEntryFinder`An abstract base class representing a [path entry finder](../glossary.xhtml#term-path-entry-finder). Though it bears some similarities to [`MetaPathFinder`](#importlib.abc.MetaPathFinder "importlib.abc.MetaPathFinder"), `PathEntryFinder`is meant for use only within the path-based import subsystem provided by `PathFinder`. This ABC is a subclass of [`Finder`](#importlib.abc.Finder "importlib.abc.Finder") for compatibility reasons only.
3\.3 新版功能.
`find_spec`(*fullname*, *target=None*)An abstract method for finding a [spec](../glossary.xhtml#term-module-spec) for the specified module. The finder will search for the module only within the [path entry](../glossary.xhtml#term-path-entry) to which it is assigned. If a spec cannot be found, `None` is returned. When passed in, `target`is a module object that the finder may use to make a more educated guess about what spec to return.
3\.4 新版功能.
`find_loader`(*fullname*)A legacy method for finding a [loader](../glossary.xhtml#term-loader) for the specified module. Returns a 2-tuple of `(loader, portion)` where `portion`is a sequence of file system locations contributing to part of a namespace package. The loader may be `None` while specifying `portion` to signify the contribution of the file system locations to a namespace package. An empty list can be used for `portion` to signify the loader is not part of a namespace package. If `loader` is `None` and `portion` is the empty list then no loader or location for a namespace package were found (i.e. failure to find anything for the module).
If [`find_spec()`](#importlib.abc.PathEntryFinder.find_spec "importlib.abc.PathEntryFinder.find_spec") is defined then backwards-compatible functionality is provided.
在 3.4 版更改: Returns `(None, [])` instead of raising [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError"). Uses [`find_spec()`](#importlib.abc.PathEntryFinder.find_spec "importlib.abc.PathEntryFinder.find_spec") when available to provide functionality.
3\.4 版后已移除: Use [`find_spec()`](#importlib.abc.PathEntryFinder.find_spec "importlib.abc.PathEntryFinder.find_spec") instead.
`find_module`(*fullname*)A concrete implementation of [`Finder.find_module()`](#importlib.abc.Finder.find_module "importlib.abc.Finder.find_module") which is equivalent to `self.find_loader(fullname)[0]`.
3\.4 版后已移除: Use [`find_spec()`](#importlib.abc.PathEntryFinder.find_spec "importlib.abc.PathEntryFinder.find_spec") instead.
`invalidate_caches`()An optional method which, when called, should invalidate any internal cache used by the finder. Used by `PathFinder.invalidate_caches()`when invalidating the caches of all cached finders.
*class* `importlib.abc.``Loader`An abstract base class for a [loader](../glossary.xhtml#term-loader). See [**PEP 302**](https://www.python.org/dev/peps/pep-0302) \[https://www.python.org/dev/peps/pep-0302\] for the exact definition for a loader.
Loaders that wish to support resource reading should implement a `get_resource_reader(fullname)` method as specified by [`importlib.abc.ResourceReader`](#importlib.abc.ResourceReader "importlib.abc.ResourceReader").
在 3.7 版更改: Introduced the optional `get_resource_reader()` method.
`create_module`(*spec*)A method that returns the module object to use when importing a module. This method may return `None`, indicating that default module creation semantics should take place.
3\.4 新版功能.
在 3.5 版更改: Starting in Python 3.6, this method will not be optional when [`exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module") is defined.
`exec_module`(*module*)An abstract method that executes the module in its own namespace when a module is imported or reloaded. The module should already be initialized when `exec_module()` is called. When this method exists, [`create_module()`](#importlib.abc.Loader.create_module "importlib.abc.Loader.create_module") must be defined.
3\.4 新版功能.
在 3.6 版更改: [`create_module()`](#importlib.abc.Loader.create_module "importlib.abc.Loader.create_module") must also be defined.
`load_module`(*fullname*)A legacy method for loading a module. If the module cannot be loaded, [`ImportError`](exceptions.xhtml#ImportError "ImportError") is raised, otherwise the loaded module is returned.
If the requested module already exists in [`sys.modules`](sys.xhtml#sys.modules "sys.modules"), that module should be used and reloaded. Otherwise the loader should create a new module and insert it into [`sys.modules`](sys.xhtml#sys.modules "sys.modules") before any loading begins, to prevent recursion from the import. If the loader inserted a module and the load fails, it must be removed by the loader from [`sys.modules`](sys.xhtml#sys.modules "sys.modules"); modules already in [`sys.modules`](sys.xhtml#sys.modules "sys.modules") before the loader began execution should be left alone (see [`importlib.util.module_for_loader()`](#importlib.util.module_for_loader "importlib.util.module_for_loader")).
The loader should set several attributes on the module. (Note that some of these attributes can change when a module is reloaded):
- [`__name__`](../reference/import.xhtml#__name__ "__name__")The name of the module.
- [`__file__`](../reference/import.xhtml#__file__ "__file__")The path to where the module data is stored (not set for built-in modules).
- [`__cached__`](../reference/import.xhtml#__cached__ "__cached__")The path to where a compiled version of the module is/should be stored (not set when the attribute would be inappropriate).
- [`__path__`](../reference/import.xhtml#__path__ "__path__")A list of strings specifying the search path within a package. This attribute is not set on modules.
- [`__package__`](../reference/import.xhtml#__package__ "__package__")The parent package for the module/package. If the module is top-level then it has a value of the empty string. The [`importlib.util.module_for_loader()`](#importlib.util.module_for_loader "importlib.util.module_for_loader") decorator can handle the details for [`__package__`](../reference/import.xhtml#__package__ "__package__").
- [`__loader__`](../reference/import.xhtml#__loader__ "__loader__")The loader used to load the module. The [`importlib.util.module_for_loader()`](#importlib.util.module_for_loader "importlib.util.module_for_loader") decorator can handle the details for [`__package__`](../reference/import.xhtml#__package__ "__package__").
When [`exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module") is available then backwards-compatible functionality is provided.
在 3.4 版更改: Raise [`ImportError`](exceptions.xhtml#ImportError "ImportError") when called instead of [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError"). Functionality provided when [`exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module") is available.
3\.4 版后已移除: The recommended API for loading a module is [`exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module")(and [`create_module()`](#importlib.abc.Loader.create_module "importlib.abc.Loader.create_module")). Loaders should implement it instead of load\_module(). The import machinery takes care of all the other responsibilities of load\_module() when exec\_module() is implemented.
`module_repr`(*module*)A legacy method which when implemented calculates and returns the given module's repr, as a string. The module type's default repr() will use the result of this method as appropriate.
3\.3 新版功能.
在 3.4 版更改: Made optional instead of an abstractmethod.
3\.4 版后已移除: The import machinery now takes care of this automatically.
*class* `importlib.abc.``ResourceReader`An [abstract base class](../glossary.xhtml#term-abstract-base-class) to provide the ability to read *resources*.
From the perspective of this ABC, a *resource* is a binary artifact that is shipped within a package. Typically this is something like a data file that lives next to the `__init__.py`file of the package. The purpose of this class is to help abstract out the accessing of such data files so that it does not matter if the package and its data file(s) are stored in a e.g. zip file versus on the file system.
For any of methods of this class, a *resource* argument is expected to be a [path-like object](../glossary.xhtml#term-path-like-object) which represents conceptually just a file name. This means that no subdirectory paths should be included in the *resource* argument. This is because the location of the package the reader is for, acts as the "directory". Hence the metaphor for directories and file names is packages and resources, respectively. This is also why instances of this class are expected to directly correlate to a specific package (instead of potentially representing multiple packages or a module).
Loaders that wish to support resource reading are expected to provide a method called `get_resource_loader(fullname)` which returns an object implementing this ABC's interface. If the module specified by fullname is not a package, this method should return [`None`](constants.xhtml#None "None"). An object compatible with this ABC should only be returned when the specified module is a package.
3\.7 新版功能.
*abstractmethod* `open_resource`(*resource*)Returns an opened, [file-like object](../glossary.xhtml#term-file-like-object) for binary reading of the *resource*.
If the resource cannot be found, [`FileNotFoundError`](exceptions.xhtml#FileNotFoundError "FileNotFoundError") is raised.
*abstractmethod* `resource_path`(*resource*)Returns the file system path to the *resource*.
If the resource does not concretely exist on the file system, raise [`FileNotFoundError`](exceptions.xhtml#FileNotFoundError "FileNotFoundError").
*abstractmethod* `is_resource`(*name*)Returns `True` if the named *name* is considered a resource. [`FileNotFoundError`](exceptions.xhtml#FileNotFoundError "FileNotFoundError") is raised if *name* does not exist.
*abstractmethod* `contents`()Returns an [iterable](../glossary.xhtml#term-iterable) of strings over the contents of the package. Do note that it is not required that all names returned by the iterator be actual resources, e.g. it is acceptable to return names for which [`is_resource()`](#importlib.abc.ResourceReader.is_resource "importlib.abc.ResourceReader.is_resource") would be false.
Allowing non-resource names to be returned is to allow for situations where how a package and its resources are stored are known a priori and the non-resource names would be useful. For instance, returning subdirectory names is allowed so that when it is known that the package and resources are stored on the file system then those subdirectory names can be used directly.
The abstract method returns an iterable of no items.
*class* `importlib.abc.``ResourceLoader`An abstract base class for a [loader](../glossary.xhtml#term-loader) which implements the optional [**PEP 302**](https://www.python.org/dev/peps/pep-0302) \[https://www.python.org/dev/peps/pep-0302\] protocol for loading arbitrary resources from the storage back-end.
3\.7 版后已移除: This ABC is deprecated in favour of supporting resource loading through [`importlib.abc.ResourceReader`](#importlib.abc.ResourceReader "importlib.abc.ResourceReader").
*abstractmethod* `get_data`(*path*)An abstract method to return the bytes for the data located at *path*. Loaders that have a file-like storage back-end that allows storing arbitrary data can implement this abstract method to give direct access to the data stored. [`OSError`](exceptions.xhtml#OSError "OSError") is to be raised if the *path* cannot be found. The *path* is expected to be constructed using a module's [`__file__`](../reference/import.xhtml#__file__ "__file__") attribute or an item from a package's [`__path__`](../reference/import.xhtml#__path__ "__path__").
在 3.4 版更改: Raises [`OSError`](exceptions.xhtml#OSError "OSError") instead of [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError").
*class* `importlib.abc.``InspectLoader`An abstract base class for a [loader](../glossary.xhtml#term-loader) which implements the optional [**PEP 302**](https://www.python.org/dev/peps/pep-0302) \[https://www.python.org/dev/peps/pep-0302\] protocol for loaders that inspect modules.
`get_code`(*fullname*)Return the code object for a module, or `None` if the module does not have a code object (as would be the case, for example, for a built-in module). Raise an [`ImportError`](exceptions.xhtml#ImportError "ImportError") if loader cannot find the requested module.
注解
While the method has a default implementation, it is suggested that it be overridden if possible for performance.
在 3.4 版更改: No longer abstract and a concrete implementation is provided.
*abstractmethod* `get_source`(*fullname*)An abstract method to return the source of a module. It is returned as a text string using [universal newlines](../glossary.xhtml#term-universal-newlines), translating all recognized line separators into `'\n'` characters. Returns `None`if no source is available (e.g. a built-in module). Raises [`ImportError`](exceptions.xhtml#ImportError "ImportError") if the loader cannot find the module specified.
在 3.4 版更改: Raises [`ImportError`](exceptions.xhtml#ImportError "ImportError") instead of [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError").
`is_package`(*fullname*)An abstract method to return a true value if the module is a package, a false value otherwise. [`ImportError`](exceptions.xhtml#ImportError "ImportError") is raised if the [loader](../glossary.xhtml#term-loader) cannot find the module.
在 3.4 版更改: Raises [`ImportError`](exceptions.xhtml#ImportError "ImportError") instead of [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError").
*static* `source_to_code`(*data*, *path='<string>'*)Create a code object from Python source.
The *data* argument can be whatever the [`compile()`](functions.xhtml#compile "compile") function supports (i.e. string or bytes). The *path* argument should be the "path" to where the source code originated from, which can be an abstract concept (e.g. location in a zip file).
With the subsequent code object one can execute it in a module by running `exec(code, module.__dict__)`.
3\.4 新版功能.
在 3.5 版更改: Made the method static.
`exec_module`(*module*)Implementation of [`Loader.exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module").
3\.4 新版功能.
`load_module`(*fullname*)Implementation of [`Loader.load_module()`](#importlib.abc.Loader.load_module "importlib.abc.Loader.load_module").
3\.4 版后已移除: use [`exec_module()`](#importlib.abc.InspectLoader.exec_module "importlib.abc.InspectLoader.exec_module") instead.
*class* `importlib.abc.``ExecutionLoader`An abstract base class which inherits from [`InspectLoader`](#importlib.abc.InspectLoader "importlib.abc.InspectLoader") that, when implemented, helps a module to be executed as a script. The ABC represents an optional [**PEP 302**](https://www.python.org/dev/peps/pep-0302) \[https://www.python.org/dev/peps/pep-0302\] protocol.
*abstractmethod* `get_filename`(*fullname*)An abstract method that is to return the value of [`__file__`](../reference/import.xhtml#__file__ "__file__") for the specified module. If no path is available, [`ImportError`](exceptions.xhtml#ImportError "ImportError") is raised.
If source code is available, then the method should return the path to the source file, regardless of whether a bytecode was used to load the module.
在 3.4 版更改: Raises [`ImportError`](exceptions.xhtml#ImportError "ImportError") instead of [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError").
*class* `importlib.abc.``FileLoader`(*fullname*, *path*)An abstract base class which inherits from [`ResourceLoader`](#importlib.abc.ResourceLoader "importlib.abc.ResourceLoader") and [`ExecutionLoader`](#importlib.abc.ExecutionLoader "importlib.abc.ExecutionLoader"), providing concrete implementations of [`ResourceLoader.get_data()`](#importlib.abc.ResourceLoader.get_data "importlib.abc.ResourceLoader.get_data") and [`ExecutionLoader.get_filename()`](#importlib.abc.ExecutionLoader.get_filename "importlib.abc.ExecutionLoader.get_filename").
The *fullname* argument is a fully resolved name of the module the loader is to handle. The *path* argument is the path to the file for the module.
3\.3 新版功能.
`name`The name of the module the loader can handle.
`path`Path to the file of the module.
`load_module`(*fullname*)Calls super's `load_module()`.
3\.4 版后已移除: Use [`Loader.exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module") instead.
*abstractmethod* `get_filename`(*fullname*)Returns [`path`](#importlib.abc.FileLoader.path "importlib.abc.FileLoader.path").
*abstractmethod* `get_data`(*path*)Reads *path* as a binary file and returns the bytes from it.
*class* `importlib.abc.``SourceLoader`An abstract base class for implementing source (and optionally bytecode) file loading. The class inherits from both [`ResourceLoader`](#importlib.abc.ResourceLoader "importlib.abc.ResourceLoader") and [`ExecutionLoader`](#importlib.abc.ExecutionLoader "importlib.abc.ExecutionLoader"), requiring the implementation of:
- [`ResourceLoader.get_data()`](#importlib.abc.ResourceLoader.get_data "importlib.abc.ResourceLoader.get_data")
- [`ExecutionLoader.get_filename()`](#importlib.abc.ExecutionLoader.get_filename "importlib.abc.ExecutionLoader.get_filename")Should only return the path to the source file; sourceless loading is not supported.
The abstract methods defined by this class are to add optional bytecode file support. Not implementing these optional methods (or causing them to raise [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError")) causes the loader to only work with source code. Implementing the methods allows the loader to work with source *and* bytecode files; it does not allow for *sourceless*loading where only bytecode is provided. Bytecode files are an optimization to speed up loading by removing the parsing step of Python's compiler, and so no bytecode-specific API is exposed.
`path_stats`(*path*)Optional abstract method which returns a [`dict`](stdtypes.xhtml#dict "dict") containing metadata about the specified path. Supported dictionary keys are:
- `'mtime'` (mandatory): an integer or floating-point number representing the modification time of the source code;
- `'size'` (optional): the size in bytes of the source code.
Any other keys in the dictionary are ignored, to allow for future extensions. If the path cannot be handled, [`OSError`](exceptions.xhtml#OSError "OSError") is raised.
3\.3 新版功能.
在 3.4 版更改: Raise [`OSError`](exceptions.xhtml#OSError "OSError") instead of [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError").
`path_mtime`(*path*)Optional abstract method which returns the modification time for the specified path.
3\.3 版后已移除: This method is deprecated in favour of [`path_stats()`](#importlib.abc.SourceLoader.path_stats "importlib.abc.SourceLoader.path_stats"). You don't have to implement it, but it is still available for compatibility purposes. Raise [`OSError`](exceptions.xhtml#OSError "OSError") if the path cannot be handled.
在 3.4 版更改: Raise [`OSError`](exceptions.xhtml#OSError "OSError") instead of [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError").
`set_data`(*path*, *data*)Optional abstract method which writes the specified bytes to a file path. Any intermediate directories which do not exist are to be created automatically.
When writing to the path fails because the path is read-only ([`errno.EACCES`](errno.xhtml#errno.EACCES "errno.EACCES")/[`PermissionError`](exceptions.xhtml#PermissionError "PermissionError")), do not propagate the exception.
在 3.4 版更改: No longer raises [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError") when called.
`get_code`(*fullname*)Concrete implementation of [`InspectLoader.get_code()`](#importlib.abc.InspectLoader.get_code "importlib.abc.InspectLoader.get_code").
`exec_module`(*module*)Concrete implementation of [`Loader.exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module").
3\.4 新版功能.
`load_module`(*fullname*)Concrete implementation of [`Loader.load_module()`](#importlib.abc.Loader.load_module "importlib.abc.Loader.load_module").
3\.4 版后已移除: Use [`exec_module()`](#importlib.abc.SourceLoader.exec_module "importlib.abc.SourceLoader.exec_module") instead.
`get_source`(*fullname*)Concrete implementation of [`InspectLoader.get_source()`](#importlib.abc.InspectLoader.get_source "importlib.abc.InspectLoader.get_source").
`is_package`(*fullname*)Concrete implementation of [`InspectLoader.is_package()`](#importlib.abc.InspectLoader.is_package "importlib.abc.InspectLoader.is_package"). A module is determined to be a package if its file path (as provided by [`ExecutionLoader.get_filename()`](#importlib.abc.ExecutionLoader.get_filename "importlib.abc.ExecutionLoader.get_filename")) is a file named `__init__` when the file extension is removed **and** the module name itself does not end in `__init__`.
## [`importlib.resources`](#module-importlib.resources "importlib.resources: Package resource reading, opening, and access") -- Resources
**Source code:** [Lib/importlib/resources.py](https://github.com/python/cpython/tree/3.7/Lib/importlib/resources.py) \[https://github.com/python/cpython/tree/3.7/Lib/importlib/resources.py\]
- - - - - -
3\.7 新版功能.
This module leverages Python's import system to provide access to *resources*within *packages*. If you can import a package, you can access resources within that package. Resources can be opened or read, in either binary or text mode.
Resources are roughly akin to files inside directories, though it's important to keep in mind that this is just a metaphor. Resources and packages **do not** have to exist as physical files and directories on the file system.
注解
This module provides functionality similar to [pkg\_resources](https://setuptools.readthedocs.io/en/latest/pkg_resources.html) \[https://setuptools.readthedocs.io/en/latest/pkg\_resources.html\] [Basic Resource Access](http://setuptools.readthedocs.io/en/latest/pkg_resources.html#basic-resource-access) \[http://setuptools.readthedocs.io/en/latest/pkg\_resources.html#basic-resource-access\]without the performance overhead of that package. This makes reading resources included in packages easier, with more stable and consistent semantics.
The standalone backport of this module provides more information on [using importlib.resources](http://importlib-resources.readthedocs.io/en/latest/using.html) \[http://importlib-resources.readthedocs.io/en/latest/using.html\] and [migrating from pkg\_resources to importlib.resources](http://importlib-resources.readthedocs.io/en/latest/migration.html) \[http://importlib-resources.readthedocs.io/en/latest/migration.html\].
Loaders that wish to support resource reading should implement a `get_resource_reader(fullname)` method as specified by [`importlib.abc.ResourceReader`](#importlib.abc.ResourceReader "importlib.abc.ResourceReader").
The following types are defined.
`importlib.resources.``Package`The `Package` type is defined as `Union[str, ModuleType]`. This means that where the function describes accepting a `Package`, you can pass in either a string or a module. Module objects must have a resolvable `__spec__.submodule_search_locations` that is not `None`.
`importlib.resources.``Resource`This type describes the resource names passed into the various functions in this package. This is defined as `Union[str, os.PathLike]`.
The following functions are available.
`importlib.resources.``open_binary`(*package*, *resource*)Open for binary reading the *resource* within *package*.
*package* is either a name or a module object which conforms to the `Package` requirements. *resource* is the name of the resource to open within *package*; it may not contain path separators and it may not have sub-resources (i.e. it cannot be a directory). This function returns a `typing.BinaryIO` instance, a binary I/O stream open for reading.
`importlib.resources.``open_text`(*package*, *resource*, *encoding='utf-8'*, *errors='strict'*)Open for text reading the *resource* within *package*. By default, the resource is opened for reading as UTF-8.
*package* is either a name or a module object which conforms to the `Package` requirements. *resource* is the name of the resource to open within *package*; it may not contain path separators and it may not have sub-resources (i.e. it cannot be a directory). *encoding* and *errors*have the same meaning as with built-in [`open()`](functions.xhtml#open "open").
This function returns a `typing.TextIO` instance, a text I/O stream open for reading.
`importlib.resources.``read_binary`(*package*, *resource*)Read and return the contents of the *resource* within *package* as `bytes`.
*package* is either a name or a module object which conforms to the `Package` requirements. *resource* is the name of the resource to open within *package*; it may not contain path separators and it may not have sub-resources (i.e. it cannot be a directory). This function returns the contents of the resource as [`bytes`](stdtypes.xhtml#bytes "bytes").
`importlib.resources.``read_text`(*package*, *resource*, *encoding='utf-8'*, *errors='strict'*)Read and return the contents of *resource* within *package* as a `str`. By default, the contents are read as strict UTF-8.
*package* is either a name or a module object which conforms to the `Package` requirements. *resource* is the name of the resource to open within *package*; it may not contain path separators and it may not have sub-resources (i.e. it cannot be a directory). *encoding* and *errors*have the same meaning as with built-in [`open()`](functions.xhtml#open "open"). This function returns the contents of the resource as [`str`](stdtypes.xhtml#str "str").
`importlib.resources.``path`(*package*, *resource*)Return the path to the *resource* as an actual file system path. This function returns a context manager for use in a [`with`](../reference/compound_stmts.xhtml#with) statement. The context manager provides a [`pathlib.Path`](pathlib.xhtml#pathlib.Path "pathlib.Path") object.
Exiting the context manager cleans up any temporary file created when the resource needs to be extracted from e.g. a zip file.
*package* is either a name or a module object which conforms to the `Package` requirements. *resource* is the name of the resource to open within *package*; it may not contain path separators and it may not have sub-resources (i.e. it cannot be a directory).
`importlib.resources.``is_resource`(*package*, *name*)Return `True` if there is a resource named *name* in the package, otherwise `False`. Remember that directories are *not* resources! *package* is either a name or a module object which conforms to the `Package` requirements.
`importlib.resources.``contents`(*package*)Return an iterable over the named items within the package. The iterable returns [`str`](stdtypes.xhtml#str "str") resources (e.g. files) and non-resources (e.g. directories). The iterable does not recurse into subdirectories.
*package* is either a name or a module object which conforms to the `Package` requirements.
## [`importlib.machinery`](#module-importlib.machinery "importlib.machinery: Importers and path hooks") -- Importers and path hooks
**Source code:** [Lib/importlib/machinery.py](https://github.com/python/cpython/tree/3.7/Lib/importlib/machinery.py) \[https://github.com/python/cpython/tree/3.7/Lib/importlib/machinery.py\]
- - - - - -
This module contains the various objects that help [`import`](../reference/simple_stmts.xhtml#import)find and load modules.
`importlib.machinery.``SOURCE_SUFFIXES`A list of strings representing the recognized file suffixes for source modules.
3\.3 新版功能.
`importlib.machinery.``DEBUG_BYTECODE_SUFFIXES`A list of strings representing the file suffixes for non-optimized bytecode modules.
3\.3 新版功能.
3\.5 版后已移除: Use [`BYTECODE_SUFFIXES`](#importlib.machinery.BYTECODE_SUFFIXES "importlib.machinery.BYTECODE_SUFFIXES") instead.
`importlib.machinery.``OPTIMIZED_BYTECODE_SUFFIXES`A list of strings representing the file suffixes for optimized bytecode modules.
3\.3 新版功能.
3\.5 版后已移除: Use [`BYTECODE_SUFFIXES`](#importlib.machinery.BYTECODE_SUFFIXES "importlib.machinery.BYTECODE_SUFFIXES") instead.
`importlib.machinery.``BYTECODE_SUFFIXES`A list of strings representing the recognized file suffixes for bytecode modules (including the leading dot).
3\.3 新版功能.
在 3.5 版更改: The value is no longer dependent on `__debug__`.
`importlib.machinery.``EXTENSION_SUFFIXES`A list of strings representing the recognized file suffixes for extension modules.
3\.3 新版功能.
`importlib.machinery.``all_suffixes`()Returns a combined list of strings representing all file suffixes for modules recognized by the standard import machinery. This is a helper for code which simply needs to know if a filesystem path potentially refers to a module without needing any details on the kind of module (for example, [`inspect.getmodulename()`](inspect.xhtml#inspect.getmodulename "inspect.getmodulename")).
3\.3 新版功能.
*class* `importlib.machinery.``BuiltinImporter`An [importer](../glossary.xhtml#term-importer) for built-in modules. All known built-in modules are listed in [`sys.builtin_module_names`](sys.xhtml#sys.builtin_module_names "sys.builtin_module_names"). This class implements the [`importlib.abc.MetaPathFinder`](#importlib.abc.MetaPathFinder "importlib.abc.MetaPathFinder") and [`importlib.abc.InspectLoader`](#importlib.abc.InspectLoader "importlib.abc.InspectLoader") ABCs.
Only class methods are defined by this class to alleviate the need for instantiation.
在 3.5 版更改: As part of [**PEP 489**](https://www.python.org/dev/peps/pep-0489) \[https://www.python.org/dev/peps/pep-0489\], the builtin importer now implements `Loader.create_module()` and `Loader.exec_module()`
*class* `importlib.machinery.``FrozenImporter`An [importer](../glossary.xhtml#term-importer) for frozen modules. This class implements the [`importlib.abc.MetaPathFinder`](#importlib.abc.MetaPathFinder "importlib.abc.MetaPathFinder") and [`importlib.abc.InspectLoader`](#importlib.abc.InspectLoader "importlib.abc.InspectLoader") ABCs.
Only class methods are defined by this class to alleviate the need for instantiation.
*class* `importlib.machinery.``WindowsRegistryFinder`[Finder](../glossary.xhtml#term-finder) for modules declared in the Windows registry. This class implements the [`importlib.abc.MetaPathFinder`](#importlib.abc.MetaPathFinder "importlib.abc.MetaPathFinder") ABC.
Only class methods are defined by this class to alleviate the need for instantiation.
3\.3 新版功能.
3\.6 版后已移除: Use [`site`](site.xhtml#module-site "site: Module responsible for site-specific configuration.") configuration instead. Future versions of Python may not enable this finder by default.
*class* `importlib.machinery.``PathFinder`A [Finder](../glossary.xhtml#term-finder) for [`sys.path`](sys.xhtml#sys.path "sys.path") and package `__path__` attributes. This class implements the [`importlib.abc.MetaPathFinder`](#importlib.abc.MetaPathFinder "importlib.abc.MetaPathFinder") ABC.
Only class methods are defined by this class to alleviate the need for instantiation.
*classmethod* `find_spec`(*fullname*, *path=None*, *target=None*)Class method that attempts to find a [spec](../glossary.xhtml#term-module-spec)for the module specified by *fullname* on [`sys.path`](sys.xhtml#sys.path "sys.path") or, if defined, on *path*. For each path entry that is searched, [`sys.path_importer_cache`](sys.xhtml#sys.path_importer_cache "sys.path_importer_cache") is checked. If a non-false object is found then it is used as the [path entry finder](../glossary.xhtml#term-path-entry-finder) to look for the module being searched for. If no entry is found in [`sys.path_importer_cache`](sys.xhtml#sys.path_importer_cache "sys.path_importer_cache"), then [`sys.path_hooks`](sys.xhtml#sys.path_hooks "sys.path_hooks") is searched for a finder for the path entry and, if found, is stored in [`sys.path_importer_cache`](sys.xhtml#sys.path_importer_cache "sys.path_importer_cache") along with being queried about the module. If no finder is ever found then `None` is both stored in the cache and returned.
3\.4 新版功能.
在 3.5 版更改: If the current working directory -- represented by an empty string -- is no longer valid then `None` is returned but no value is cached in [`sys.path_importer_cache`](sys.xhtml#sys.path_importer_cache "sys.path_importer_cache").
*classmethod* `find_module`(*fullname*, *path=None*)A legacy wrapper around [`find_spec()`](#importlib.machinery.PathFinder.find_spec "importlib.machinery.PathFinder.find_spec").
3\.4 版后已移除: Use [`find_spec()`](#importlib.machinery.PathFinder.find_spec "importlib.machinery.PathFinder.find_spec") instead.
*classmethod* `invalidate_caches`()Calls [`importlib.abc.PathEntryFinder.invalidate_caches()`](#importlib.abc.PathEntryFinder.invalidate_caches "importlib.abc.PathEntryFinder.invalidate_caches") on all finders stored in [`sys.path_importer_cache`](sys.xhtml#sys.path_importer_cache "sys.path_importer_cache") that define the method. Otherwise entries in [`sys.path_importer_cache`](sys.xhtml#sys.path_importer_cache "sys.path_importer_cache") set to `None` are deleted.
在 3.7 版更改: Entries of `None` in [`sys.path_importer_cache`](sys.xhtml#sys.path_importer_cache "sys.path_importer_cache") are deleted.
在 3.4 版更改: Calls objects in [`sys.path_hooks`](sys.xhtml#sys.path_hooks "sys.path_hooks") with the current working directory for `''` (i.e. the empty string).
*class* `importlib.machinery.``FileFinder`(*path*, *\*loader\_details*)A concrete implementation of [`importlib.abc.PathEntryFinder`](#importlib.abc.PathEntryFinder "importlib.abc.PathEntryFinder") which caches results from the file system.
The *path* argument is the directory for which the finder is in charge of searching.
The *loader\_details* argument is a variable number of 2-item tuples each containing a loader and a sequence of file suffixes the loader recognizes. The loaders are expected to be callables which accept two arguments of the module's name and the path to the file found.
The finder will cache the directory contents as necessary, making stat calls for each module search to verify the cache is not outdated. Because cache staleness relies upon the granularity of the operating system's state information of the file system, there is a potential race condition of searching for a module, creating a new file, and then searching for the module the new file represents. If the operations happen fast enough to fit within the granularity of stat calls, then the module search will fail. To prevent this from happening, when you create a module dynamically, make sure to call [`importlib.invalidate_caches()`](#importlib.invalidate_caches "importlib.invalidate_caches").
3\.3 新版功能.
`path`The path the finder will search in.
`find_spec`(*fullname*, *target=None*)Attempt to find the spec to handle *fullname* within [`path`](#importlib.machinery.FileFinder.path "importlib.machinery.FileFinder.path").
3\.4 新版功能.
`find_loader`(*fullname*)Attempt to find the loader to handle *fullname* within [`path`](#importlib.machinery.FileFinder.path "importlib.machinery.FileFinder.path").
`invalidate_caches`()Clear out the internal cache.
*classmethod* `path_hook`(*\*loader\_details*)A class method which returns a closure for use on [`sys.path_hooks`](sys.xhtml#sys.path_hooks "sys.path_hooks"). An instance of [`FileFinder`](#importlib.machinery.FileFinder "importlib.machinery.FileFinder") is returned by the closure using the path argument given to the closure directly and *loader\_details*indirectly.
If the argument to the closure is not an existing directory, [`ImportError`](exceptions.xhtml#ImportError "ImportError") is raised.
*class* `importlib.machinery.``SourceFileLoader`(*fullname*, *path*)A concrete implementation of [`importlib.abc.SourceLoader`](#importlib.abc.SourceLoader "importlib.abc.SourceLoader") by subclassing [`importlib.abc.FileLoader`](#importlib.abc.FileLoader "importlib.abc.FileLoader") and providing some concrete implementations of other methods.
3\.3 新版功能.
`name`The name of the module that this loader will handle.
`path`The path to the source file.
`is_package`(*fullname*)Return true if [`path`](#importlib.machinery.SourceFileLoader.path "importlib.machinery.SourceFileLoader.path") appears to be for a package.
`path_stats`(*path*)Concrete implementation of [`importlib.abc.SourceLoader.path_stats()`](#importlib.abc.SourceLoader.path_stats "importlib.abc.SourceLoader.path_stats").
`set_data`(*path*, *data*)Concrete implementation of [`importlib.abc.SourceLoader.set_data()`](#importlib.abc.SourceLoader.set_data "importlib.abc.SourceLoader.set_data").
`load_module`(*name=None*)Concrete implementation of [`importlib.abc.Loader.load_module()`](#importlib.abc.Loader.load_module "importlib.abc.Loader.load_module") where specifying the name of the module to load is optional.
3\.6 版后已移除: Use [`importlib.abc.Loader.exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module") instead.
*class* `importlib.machinery.``SourcelessFileLoader`(*fullname*, *path*)A concrete implementation of [`importlib.abc.FileLoader`](#importlib.abc.FileLoader "importlib.abc.FileLoader") which can import bytecode files (i.e. no source code files exist).
Please note that direct use of bytecode files (and thus not source code files) inhibits your modules from being usable by all Python implementations or new versions of Python which change the bytecode format.
3\.3 新版功能.
`name`The name of the module the loader will handle.
`path`The path to the bytecode file.
`is_package`(*fullname*)Determines if the module is a package based on [`path`](#importlib.machinery.SourcelessFileLoader.path "importlib.machinery.SourcelessFileLoader.path").
`get_code`(*fullname*)Returns the code object for [`name`](#importlib.machinery.SourcelessFileLoader.name "importlib.machinery.SourcelessFileLoader.name") created from [`path`](#importlib.machinery.SourcelessFileLoader.path "importlib.machinery.SourcelessFileLoader.path").
`get_source`(*fullname*)Returns `None` as bytecode files have no source when this loader is used.
`load_module`(*name=None*)Concrete implementation of [`importlib.abc.Loader.load_module()`](#importlib.abc.Loader.load_module "importlib.abc.Loader.load_module") where specifying the name of the module to load is optional.
3\.6 版后已移除: Use [`importlib.abc.Loader.exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module") instead.
*class* `importlib.machinery.``ExtensionFileLoader`(*fullname*, *path*)A concrete implementation of [`importlib.abc.ExecutionLoader`](#importlib.abc.ExecutionLoader "importlib.abc.ExecutionLoader") for extension modules.
The *fullname* argument specifies the name of the module the loader is to support. The *path* argument is the path to the extension module's file.
3\.3 新版功能.
`name`Name of the module the loader supports.
`path`Path to the extension module.
`create_module`(*spec*)Creates the module object from the given specification in accordance with [**PEP 489**](https://www.python.org/dev/peps/pep-0489) \[https://www.python.org/dev/peps/pep-0489\].
3\.5 新版功能.
`exec_module`(*module*)Initializes the given module object in accordance with [**PEP 489**](https://www.python.org/dev/peps/pep-0489) \[https://www.python.org/dev/peps/pep-0489\].
3\.5 新版功能.
`is_package`(*fullname*)Returns `True` if the file path points to a package's `__init__`module based on [`EXTENSION_SUFFIXES`](#importlib.machinery.EXTENSION_SUFFIXES "importlib.machinery.EXTENSION_SUFFIXES").
`get_code`(*fullname*)Returns `None` as extension modules lack a code object.
`get_source`(*fullname*)Returns `None` as extension modules do not have source code.
`get_filename`(*fullname*)Returns [`path`](#importlib.machinery.ExtensionFileLoader.path "importlib.machinery.ExtensionFileLoader.path").
3\.4 新版功能.
*class* `importlib.machinery.``ModuleSpec`(*name*, *loader*, *\**, *origin=None*, *loader\_state=None*, *is\_package=None*)A specification for a module's import-system-related state. This is typically exposed as the module's `__spec__` attribute. In the descriptions below, the names in parentheses give the corresponding attribute available directly on the module object. E.g. `module.__spec__.origin == module.__file__`. Note however that while the *values* are usually equivalent, they can differ since there is no synchronization between the two objects. Thus it is possible to update the module's `__path__` at runtime, and this will not be automatically reflected in `__spec__.submodule_search_locations`.
3\.4 新版功能.
`name`(`__name__`)
A string for the fully-qualified name of the module.
`loader`(`__loader__`)
The loader to use for loading. For namespace packages this should be set to `None`.
`origin`(`__file__`)
Name of the place from which the module is loaded, e.g. "builtin" for built-in modules and the filename for modules loaded from source. Normally "origin" should be set, but it may be `None` (the default) which indicates it is unspecified (e.g. for namespace packages).
`submodule_search_locations`(`__path__`)
List of strings for where to find submodules, if a package (`None`otherwise).
`loader_state`Container of extra module-specific data for use during loading (or `None`).
`cached`(`__cached__`)
String for where the compiled module should be stored (or `None`).
`parent`(`__package__`)
(Read-only) Fully-qualified name of the package to which the module belongs as a submodule (or `None`).
`has_location`Boolean indicating whether or not the module's "origin" attribute refers to a loadable location.
## [`importlib.util`](#module-importlib.util "importlib.util: Utility code for importers") -- Utility code for importers
**Source code:** [Lib/importlib/util.py](https://github.com/python/cpython/tree/3.7/Lib/importlib/util.py) \[https://github.com/python/cpython/tree/3.7/Lib/importlib/util.py\]
- - - - - -
This module contains the various objects that help in the construction of an [importer](../glossary.xhtml#term-importer).
`importlib.util.``MAGIC_NUMBER`The bytes which represent the bytecode version number. If you need help with loading/writing bytecode then consider [`importlib.abc.SourceLoader`](#importlib.abc.SourceLoader "importlib.abc.SourceLoader").
3\.4 新版功能.
`importlib.util.``cache_from_source`(*path*, *debug\_override=None*, *\**, *optimization=None*)Return the [**PEP 3147**](https://www.python.org/dev/peps/pep-3147) \[https://www.python.org/dev/peps/pep-3147\]/[**PEP 488**](https://www.python.org/dev/peps/pep-0488) \[https://www.python.org/dev/peps/pep-0488\] path to the byte-compiled file associated with the source *path*. For example, if *path* is `/foo/bar/baz.py` the return value would be `/foo/bar/__pycache__/baz.cpython-32.pyc` for Python 3.2. The `cpython-32` string comes from the current magic tag (see `get_tag()`; if `sys.implementation.cache_tag` is not defined then [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError") will be raised).
The *optimization* parameter is used to specify the optimization level of the bytecode file. An empty string represents no optimization, so `/foo/bar/baz.py` with an *optimization* of `''` will result in a bytecode path of `/foo/bar/__pycache__/baz.cpython-32.pyc`. `None` causes the interpter's optimization level to be used. Any other value's string representation being used, so `/foo/bar/baz.py` with an *optimization* of `2` will lead to the bytecode path of `/foo/bar/__pycache__/baz.cpython-32.opt-2.pyc`. The string representation of *optimization* can only be alphanumeric, else [`ValueError`](exceptions.xhtml#ValueError "ValueError") is raised.
The *debug\_override* parameter is deprecated and can be used to override the system's value for `__debug__`. A `True` value is the equivalent of setting *optimization* to the empty string. A `False` value is the same as setting *optimization* to `1`. If both *debug\_override* an *optimization*are not `None` then [`TypeError`](exceptions.xhtml#TypeError "TypeError") is raised.
3\.4 新版功能.
在 3.5 版更改: The *optimization* parameter was added and the *debug\_override* parameter was deprecated.
在 3.6 版更改: 接受一个 [类路径对象](../glossary.xhtml#term-path-like-object)。
`importlib.util.``source_from_cache`(*path*)Given the *path* to a [**PEP 3147**](https://www.python.org/dev/peps/pep-3147) \[https://www.python.org/dev/peps/pep-3147\] file name, return the associated source code file path. For example, if *path* is `/foo/bar/__pycache__/baz.cpython-32.pyc` the returned path would be `/foo/bar/baz.py`. *path* need not exist, however if it does not conform to [**PEP 3147**](https://www.python.org/dev/peps/pep-3147) \[https://www.python.org/dev/peps/pep-3147\] or [**PEP 488**](https://www.python.org/dev/peps/pep-0488) \[https://www.python.org/dev/peps/pep-0488\] format, a [`ValueError`](exceptions.xhtml#ValueError "ValueError") is raised. If `sys.implementation.cache_tag` is not defined, [`NotImplementedError`](exceptions.xhtml#NotImplementedError "NotImplementedError") is raised.
3\.4 新版功能.
在 3.6 版更改: 接受一个 [类路径对象](../glossary.xhtml#term-path-like-object)。
`importlib.util.``decode_source`(*source\_bytes*)Decode the given bytes representing source code and return it as a string with universal newlines (as required by [`importlib.abc.InspectLoader.get_source()`](#importlib.abc.InspectLoader.get_source "importlib.abc.InspectLoader.get_source")).
3\.4 新版功能.
`importlib.util.``resolve_name`(*name*, *package*)Resolve a relative module name to an absolute one.
If **name** has no leading dots, then **name** is simply returned. This allows for usage such as `importlib.util.resolve_name('sys', __package__)` without doing a check to see if the **package** argument is needed.
[`ValueError`](exceptions.xhtml#ValueError "ValueError") is raised if **name** is a relative module name but package is a false value (e.g. `None` or the empty string). [`ValueError`](exceptions.xhtml#ValueError "ValueError") is also raised a relative name would escape its containing package (e.g. requesting `..bacon` from within the `spam` package).
3\.3 新版功能.
`importlib.util.``find_spec`(*name*, *package=None*)Find the [spec](../glossary.xhtml#term-module-spec) for a module, optionally relative to the specified **package** name. If the module is in [`sys.modules`](sys.xhtml#sys.modules "sys.modules"), then `sys.modules[name].__spec__` is returned (unless the spec would be `None` or is not set, in which case [`ValueError`](exceptions.xhtml#ValueError "ValueError") is raised). Otherwise a search using [`sys.meta_path`](sys.xhtml#sys.meta_path "sys.meta_path") is done. `None` is returned if no spec is found.
If **name** is for a submodule (contains a dot), the parent module is automatically imported.
**name** and **package** work the same as for `import_module()`.
3\.4 新版功能.
在 3.7 版更改: Raises [`ModuleNotFoundError`](exceptions.xhtml#ModuleNotFoundError "ModuleNotFoundError") instead of [`AttributeError`](exceptions.xhtml#AttributeError "AttributeError") if **package** is in fact not a package (i.e. lacks a [`__path__`](../reference/import.xhtml#__path__ "__path__")attribute).
`importlib.util.``module_from_spec`(*spec*)Create a new module based on **spec** and [`spec.loader.create_module`](#importlib.abc.Loader.create_module "importlib.abc.Loader.create_module").
If [`spec.loader.create_module`](#importlib.abc.Loader.create_module "importlib.abc.Loader.create_module")does not return `None`, then any pre-existing attributes will not be reset. Also, no [`AttributeError`](exceptions.xhtml#AttributeError "AttributeError") will be raised if triggered while accessing **spec** or setting an attribute on the module.
This function is preferred over using [`types.ModuleType`](types.xhtml#types.ModuleType "types.ModuleType") to create a new module as **spec** is used to set as many import-controlled attributes on the module as possible.
3\.5 新版功能.
`@``importlib.util.``module_for_loader`A [decorator](../glossary.xhtml#term-decorator) for [`importlib.abc.Loader.load_module()`](#importlib.abc.Loader.load_module "importlib.abc.Loader.load_module")to handle selecting the proper module object to load with. The decorated method is expected to have a call signature taking two positional arguments (e.g. `load_module(self, module)`) for which the second argument will be the module **object** to be used by the loader. Note that the decorator will not work on static methods because of the assumption of two arguments.
The decorated method will take in the **name** of the module to be loaded as expected for a [loader](../glossary.xhtml#term-loader). If the module is not found in [`sys.modules`](sys.xhtml#sys.modules "sys.modules") then a new one is constructed. Regardless of where the module came from, [`__loader__`](../reference/import.xhtml#__loader__ "__loader__") set to **self** and [`__package__`](../reference/import.xhtml#__package__ "__package__")is set based on what [`importlib.abc.InspectLoader.is_package()`](#importlib.abc.InspectLoader.is_package "importlib.abc.InspectLoader.is_package") returns (if available). These attributes are set unconditionally to support reloading.
If an exception is raised by the decorated method and a module was added to [`sys.modules`](sys.xhtml#sys.modules "sys.modules"), then the module will be removed to prevent a partially initialized module from being in left in [`sys.modules`](sys.xhtml#sys.modules "sys.modules"). If the module was already in [`sys.modules`](sys.xhtml#sys.modules "sys.modules") then it is left alone.
在 3.3 版更改: [`__loader__`](../reference/import.xhtml#__loader__ "__loader__") and [`__package__`](../reference/import.xhtml#__package__ "__package__") are automatically set (when possible).
在 3.4 版更改: Set [`__name__`](../reference/import.xhtml#__name__ "__name__"), [`__loader__`](../reference/import.xhtml#__loader__ "__loader__") [`__package__`](../reference/import.xhtml#__package__ "__package__")unconditionally to support reloading.
3\.4 版后已移除: The import machinery now directly performs all the functionality provided by this function.
`@``importlib.util.``set_loader`A [decorator](../glossary.xhtml#term-decorator) for [`importlib.abc.Loader.load_module()`](#importlib.abc.Loader.load_module "importlib.abc.Loader.load_module")to set the [`__loader__`](../reference/import.xhtml#__loader__ "__loader__")attribute on the returned module. If the attribute is already set the decorator does nothing. It is assumed that the first positional argument to the wrapped method (i.e. `self`) is what [`__loader__`](../reference/import.xhtml#__loader__ "__loader__") should be set to.
在 3.4 版更改: Set `__loader__` if set to `None`, as if the attribute does not exist.
3\.4 版后已移除: The import machinery takes care of this automatically.
`@``importlib.util.``set_package`A [decorator](../glossary.xhtml#term-decorator) for [`importlib.abc.Loader.load_module()`](#importlib.abc.Loader.load_module "importlib.abc.Loader.load_module") to set the [`__package__`](../reference/import.xhtml#__package__ "__package__") attribute on the returned module. If [`__package__`](../reference/import.xhtml#__package__ "__package__")is set and has a value other than `None` it will not be changed.
3\.4 版后已移除: The import machinery takes care of this automatically.
`importlib.util.``spec_from_loader`(*name*, *loader*, *\**, *origin=None*, *is\_package=None*)A factory function for creating a `ModuleSpec` instance based on a loader. The parameters have the same meaning as they do for ModuleSpec. The function uses available [loader](../glossary.xhtml#term-loader) APIs, such as `InspectLoader.is_package()`, to fill in any missing information on the spec.
3\.4 新版功能.
`importlib.util.``spec_from_file_location`(*name*, *location*, *\**, *loader=None*, *submodule\_search\_locations=None*)A factory function for creating a `ModuleSpec` instance based on the path to a file. Missing information will be filled in on the spec by making use of loader APIs and by the implication that the module will be file-based.
3\.4 新版功能.
在 3.6 版更改: 接受一个 [类路径对象](../glossary.xhtml#term-path-like-object)。
`importlib.util.``source_hash`(*source\_bytes*)Return the hash of *source\_bytes* as bytes. A hash-based `.pyc` file embeds the [`source_hash()`](#importlib.util.source_hash "importlib.util.source_hash") of the corresponding source file's contents in its header.
3\.7 新版功能.
*class* `importlib.util.``LazyLoader`(*loader*)A class which postpones the execution of the loader of a module until the module has an attribute accessed.
This class **only** works with loaders that define [`exec_module()`](#importlib.abc.Loader.exec_module "importlib.abc.Loader.exec_module") as control over what module type is used for the module is required. For those same reasons, the loader's [`create_module()`](#importlib.abc.Loader.create_module "importlib.abc.Loader.create_module") method must return `None` or a type for which its `__class__` attribute can be mutated along with not using [slots](../glossary.xhtml#term-slots). Finally, modules which substitute the object placed into [`sys.modules`](sys.xhtml#sys.modules "sys.modules") will not work as there is no way to properly replace the module references throughout the interpreter safely; [`ValueError`](exceptions.xhtml#ValueError "ValueError") is raised if such a substitution is detected.
注解
For projects where startup time is critical, this class allows for potentially minimizing the cost of loading a module if it is never used. For projects where startup time is not essential then use of this class is **heavily** discouraged due to error messages created during loading being postponed and thus occurring out of context.
3\.5 新版功能.
在 3.6 版更改: Began calling [`create_module()`](#importlib.abc.Loader.create_module "importlib.abc.Loader.create_module"), removing the compatibility warning for [`importlib.machinery.BuiltinImporter`](#importlib.machinery.BuiltinImporter "importlib.machinery.BuiltinImporter") and [`importlib.machinery.ExtensionFileLoader`](#importlib.machinery.ExtensionFileLoader "importlib.machinery.ExtensionFileLoader").
*classmethod* `factory`(*loader*)A static method which returns a callable that creates a lazy loader. This is meant to be used in situations where the loader is passed by class instead of by instance.
```
suffixes = importlib.machinery.SOURCE_SUFFIXES
loader = importlib.machinery.SourceFileLoader
lazy_loader = importlib.util.LazyLoader.factory(loader)
finder = importlib.machinery.FileFinder(path, (lazy_loader, suffixes))
```
## 示例
### Importing programmatically
To programmatically import a module, use [`importlib.import_module()`](#importlib.import_module "importlib.import_module").
```
import importlib
itertools = importlib.import_module('itertools')
```
### Checking if a module can be imported
If you need to find out if a module can be imported without actually doing the import, then you should use [`importlib.util.find_spec()`](#importlib.util.find_spec "importlib.util.find_spec").
```
import importlib.util
import sys
# For illustrative purposes.
name = 'itertools'
spec = importlib.util.find_spec(name)
if spec is None:
print("can't find the itertools module")
else:
# If you chose to perform the actual import ...
module = importlib.util.module_from_spec(spec)
spec.loader.exec_module(module)
# Adding the module to sys.modules is optional.
sys.modules[name] = module
```
### Importing a source file directly
To import a Python source file directly, use the following recipe (Python 3.5 and newer only):
```
import importlib.util
import sys
# For illustrative purposes.
import tokenize
file_path = tokenize.__file__
module_name = tokenize.__name__
spec = importlib.util.spec_from_file_location(module_name, file_path)
module = importlib.util.module_from_spec(spec)
spec.loader.exec_module(module)
# Optional; only necessary if you want to be able to import the module
# by name later.
sys.modules[module_name] = module
```
### Setting up an importer
For deep customizations of import, you typically want to implement an [importer](../glossary.xhtml#term-importer). This means managing both the [finder](../glossary.xhtml#term-finder) and [loader](../glossary.xhtml#term-loader)side of things. For finders there are two flavours to choose from depending on your needs: a [meta path finder](../glossary.xhtml#term-meta-path-finder) or a [path entry finder](../glossary.xhtml#term-path-entry-finder). The former is what you would put on [`sys.meta_path`](sys.xhtml#sys.meta_path "sys.meta_path") while the latter is what you create using a [path entry hook](../glossary.xhtml#term-path-entry-hook) on [`sys.path_hooks`](sys.xhtml#sys.path_hooks "sys.path_hooks") which works with [`sys.path`](sys.xhtml#sys.path "sys.path") entries to potentially create a finder. This example will show you how to register your own importers so that import will use them (for creating an importer for yourself, read the documentation for the appropriate classes defined within this package):
```
import importlib.machinery
import sys
# For illustrative purposes only.
SpamMetaPathFinder = importlib.machinery.PathFinder
SpamPathEntryFinder = importlib.machinery.FileFinder
loader_details = (importlib.machinery.SourceFileLoader,
importlib.machinery.SOURCE_SUFFIXES)
# Setting up a meta path finder.
# Make sure to put the finder in the proper location in the list in terms of
# priority.
sys.meta_path.append(SpamMetaPathFinder)
# Setting up a path entry finder.
# Make sure to put the path hook in the proper location in the list in terms
# of priority.
sys.path_hooks.append(SpamPathEntryFinder.path_hook(loader_details))
```
### Approximating [`importlib.import_module()`](#importlib.import_module "importlib.import_module")
Import itself is implemented in Python code, making it possible to expose most of the import machinery through importlib. The following helps illustrate the various APIs that importlib exposes by providing an approximate implementation of [`importlib.import_module()`](#importlib.import_module "importlib.import_module") (Python 3.4 and newer for the importlib usage, Python 3.6 and newer for other parts of the code).
```
import importlib.util
import sys
def import_module(name, package=None):
"""An approximate implementation of import."""
absolute_name = importlib.util.resolve_name(name, package)
try:
return sys.modules[absolute_name]
except KeyError:
pass
path = None
if '.' in absolute_name:
parent_name, _, child_name = absolute_name.rpartition('.')
parent_module = import_module(parent_name)
path = parent_module.__spec__.submodule_search_locations
for finder in sys.meta_path:
spec = finder.find_spec(absolute_name, path)
if spec is not None:
break
else:
msg = f'No module named {absolute_name!r}'
raise ModuleNotFoundError(msg, name=absolute_name)
module = importlib.util.module_from_spec(spec)
spec.loader.exec_module(module)
sys.modules[absolute_name] = module
if path is not None:
setattr(parent_module, child_name, module)
return module
```
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- PEP 307: Pickle Enhancements
- Extended Slices
- 其他语言特性修改
- New, Improved, and Deprecated Modules
- Pymalloc: A Specialized Object Allocator
- Build and C API Changes
- Other Changes and Fixes
- Porting to Python 2.3
- Acknowledgements
- What's New in Python 2.2
- 概述
- PEPs 252 and 253: Type and Class Changes
- PEP 234: Iterators
- PEP 255: Simple Generators
- PEP 237: Unifying Long Integers and Integers
- PEP 238: Changing the Division Operator
- Unicode Changes
- PEP 227: Nested Scopes
- New and Improved Modules
- Interpreter Changes and Fixes
- Other Changes and Fixes
- Acknowledgements
- What's New in Python 2.1
- 概述
- PEP 227: Nested Scopes
- PEP 236: future Directives
- PEP 207: Rich Comparisons
- PEP 230: Warning Framework
- PEP 229: New Build System
- PEP 205: Weak References
- PEP 232: Function Attributes
- PEP 235: Importing Modules on Case-Insensitive Platforms
- PEP 217: Interactive Display Hook
- PEP 208: New Coercion Model
- PEP 241: Metadata in Python Packages
- New and Improved Modules
- Other Changes and Fixes
- Acknowledgements
- What's New in Python 2.0
- 概述
- What About Python 1.6?
- New Development Process
- Unicode
- 列表推导式
- Augmented Assignment
- 字符串的方法
- Garbage Collection of Cycles
- Other Core Changes
- Porting to 2.0
- Extending/Embedding Changes
- Distutils: Making Modules Easy to Install
- XML Modules
- Module changes
- New modules
- IDLE Improvements
- Deleted and Deprecated Modules
- Acknowledgements
- 更新日志
- Python 下一版
- Python 3.7.3 最终版
- Python 3.7.3 发布候选版 1
- Python 3.7.2 最终版
- Python 3.7.2 发布候选版 1
- Python 3.7.1 最终版
- Python 3.7.1 RC 2版本
- Python 3.7.1 发布候选版 1
- Python 3.7.0 正式版
- Python 3.7.0 release candidate 1
- Python 3.7.0 beta 5
- Python 3.7.0 beta 4
- Python 3.7.0 beta 3
- Python 3.7.0 beta 2
- Python 3.7.0 beta 1
- Python 3.7.0 alpha 4
- Python 3.7.0 alpha 3
- Python 3.7.0 alpha 2
- Python 3.7.0 alpha 1
- Python 3.6.6 final
- Python 3.6.6 RC 1
- Python 3.6.5 final
- Python 3.6.5 release candidate 1
- Python 3.6.4 final
- Python 3.6.4 release candidate 1
- Python 3.6.3 final
- Python 3.6.3 release candidate 1
- Python 3.6.2 final
- Python 3.6.2 release candidate 2
- Python 3.6.2 release candidate 1
- Python 3.6.1 final
- Python 3.6.1 release candidate 1
- Python 3.6.0 final
- Python 3.6.0 release candidate 2
- Python 3.6.0 release candidate 1
- Python 3.6.0 beta 4
- Python 3.6.0 beta 3
- Python 3.6.0 beta 2
- Python 3.6.0 beta 1
- Python 3.6.0 alpha 4
- Python 3.6.0 alpha 3
- Python 3.6.0 alpha 2
- Python 3.6.0 alpha 1
- Python 3.5.5 final
- Python 3.5.5 release candidate 1
- Python 3.5.4 final
- Python 3.5.4 release candidate 1
- Python 3.5.3 final
- Python 3.5.3 release candidate 1
- Python 3.5.2 final
- Python 3.5.2 release candidate 1
- Python 3.5.1 final
- Python 3.5.1 release candidate 1
- Python 3.5.0 final
- Python 3.5.0 release candidate 4
- Python 3.5.0 release candidate 3
- Python 3.5.0 release candidate 2
- Python 3.5.0 release candidate 1
- Python 3.5.0 beta 4
- Python 3.5.0 beta 3
- Python 3.5.0 beta 2
- Python 3.5.0 beta 1
- Python 3.5.0 alpha 4
- Python 3.5.0 alpha 3
- Python 3.5.0 alpha 2
- Python 3.5.0 alpha 1
- Python 教程
- 课前甜点
- 使用 Python 解释器
- 调用解释器
- 解释器的运行环境
- Python 的非正式介绍
- Python 作为计算器使用
- 走向编程的第一步
- 其他流程控制工具
- if 语句
- for 语句
- range() 函数
- break 和 continue 语句，以及循环中的 else 子句
- pass 语句
- 定义函数
- 函数定义的更多形式
- 小插曲：编码风格
- 数据结构
- 列表的更多特性
- del 语句
- 元组和序列
- 集合
- 字典
- 循环的技巧
- 深入条件控制
- 序列和其它类型的比较
- 模块
- 有关模块的更多信息
- 标准模块
- dir() 函数
- 包
- 输入输出
- 更漂亮的输出格式
- 读写文件
- 错误和异常
- 语法错误
- 异常
- 处理异常
- 抛出异常
- 用户自定义异常
- 定义清理操作
- 预定义的清理操作
- 类
- 名称和对象
- Python 作用域和命名空间
- 初探类
- 补充说明
- 继承
- 私有变量
- 杂项说明
- 迭代器
- 生成器
- 生成器表达式
- 标准库简介
- 操作系统接口
- 文件通配符
- 命令行参数
- 错误输出重定向和程序终止
- 字符串模式匹配
- 数学
- 互联网访问
- 日期和时间
- 数据压缩
- 性能测量
- 质量控制
- 自带电池
- 标准库简介 —— 第二部分
- 格式化输出
- 模板
- 使用二进制数据记录格式
- 多线程
- 日志
- 弱引用
- 用于操作列表的工具
- 十进制浮点运算
- 虚拟环境和包
- 概述
- 创建虚拟环境
- 使用pip管理包
- 接下来？
- 交互式编辑和编辑历史
- Tab 补全和编辑历史
- 默认交互式解释器的替代品
- 浮点算术：争议和限制
- 表示性错误
- 附录
- 交互模式
- 安装和使用 Python
- 命令行与环境
- 命令行
- 环境变量
- 在Unix平台中使用Python
- 获取最新版本的Python
- 构建Python
- 与Python相关的路径和文件
- 杂项
- 编辑器和集成开发环境
- 在Windows上使用 Python
- 完整安装程序
- Microsoft Store包
- nuget.org 安装包
- 可嵌入的包
- 替代捆绑包
- 配置Python
- 适用于Windows的Python启动器
- 查找模块
- 附加模块
- 在Windows上编译Python
- 其他平台
- 在苹果系统上使用 Python
- 获取和安装 MacPython
- IDE
- 安装额外的 Python 包
- Mac 上的图形界面编程
- 在 Mac 上分发 Python 应用程序
- 其他资源
- Python 语言参考
- 概述
- 其他实现
- 标注
- 词法分析
- 行结构
- 其他形符
- 标识符和关键字
- 字面值
- 运算符
- 分隔符
- 数据模型
- 对象、值与类型
- 标准类型层级结构
- 特殊方法名称
- 协程
- 执行模型
- 程序的结构
- 命名与绑定
- 异常
- 导入系统
- importlib
- 包
- 搜索
- 加载
- 基于路径的查找器
- 替换标准导入系统
- Package Relative Imports
- 有关 main 的特殊事项
- 开放问题项
- 参考文献
- 表达式
- 算术转换
- 原子
- 原型
- await 表达式
- 幂运算符
- 一元算术和位运算
- 二元算术运算符
- 移位运算
- 二元位运算
- 比较运算
- 布尔运算
- 条件表达式
- lambda 表达式
- 表达式列表
- 求值顺序
- 运算符优先级
- 简单语句
- 表达式语句
- 赋值语句
- assert 语句
- pass 语句
- del 语句
- return 语句
- yield 语句
- raise 语句
- break 语句
- continue 语句
- import 语句
- global 语句
- nonlocal 语句
- 复合语句
- if 语句
- while 语句
- for 语句
- try 语句
- with 语句
- 函数定义
- 类定义
- 协程
- 最高层级组件
- 完整的 Python 程序
- 文件输入
- 交互式输入
- 表达式输入
- 完整的语法规范
- Python 标准库
- 概述
- 可用性注释
- 内置函数
- 内置常量
- 由 site 模块添加的常量
- 内置类型
- 逻辑值检测
- 布尔运算 — and, or, not
- 比较
- 数字类型 — int, float, complex
- 迭代器类型
- 序列类型 — list, tuple, range
- 文本序列类型 — str
- 二进制序列类型 — bytes, bytearray, memoryview
- 集合类型 — set, frozenset
- 映射类型 — dict
- 上下文管理器类型
- 其他内置类型
- 特殊属性
- 内置异常
- 基类
- 具体异常
- 警告
- 异常层次结构
- 文本处理服务
- string — 常见的字符串操作
- re — 正则表达式操作
- 模块 difflib 是一个计算差异的助手
- textwrap — Text wrapping and filling
- unicodedata — Unicode 数据库
- stringprep — Internet String Preparation
- readline — GNU readline interface
- rlcompleter — GNU readline的完成函数
- 二进制数据服务
- struct — Interpret bytes as packed binary data
- codecs — Codec registry and base classes
- 数据类型
- datetime — 基础日期/时间数据类型
- calendar — General calendar-related functions
- collections — 容器数据类型
- collections.abc — 容器的抽象基类
- heapq — 堆队列算法
- bisect — Array bisection algorithm
- array — Efficient arrays of numeric values
- weakref — 弱引用
- types — Dynamic type creation and names for built-in types
- copy — 浅层 (shallow) 和深层 (deep) 复制操作
- pprint — 数据美化输出
- reprlib — Alternate repr() implementation
- enum — Support for enumerations
- 数字和数学模块
- numbers — 数字的抽象基类
- math — 数学函数
- cmath — Mathematical functions for complex numbers
- decimal — 十进制定点和浮点运算
- fractions — 分数
- random — 生成伪随机数
- statistics — Mathematical statistics functions
- 函数式编程模块
- itertools — 为高效循环而创建迭代器的函数
- functools — 高阶函数和可调用对象上的操作
- operator — 标准运算符替代函数
- 文件和目录访问
- pathlib — 面向对象的文件系统路径
- os.path — 常见路径操作
- fileinput — Iterate over lines from multiple input streams
- stat — Interpreting stat() results
- filecmp — File and Directory Comparisons
- tempfile — Generate temporary files and directories
- glob — Unix style pathname pattern expansion
- fnmatch — Unix filename pattern matching
- linecache — Random access to text lines
- shutil — High-level file operations
- macpath — Mac OS 9 路径操作函数
- 数据持久化
- pickle —— Python 对象序列化
- copyreg — Register pickle support functions
- shelve — Python object persistence
- marshal — Internal Python object serialization
- dbm — Interfaces to Unix “databases”
- sqlite3 — SQLite 数据库 DB-API 2.0 接口模块
- 数据压缩和存档
- zlib — 与 gzip 兼容的压缩
- gzip — 对 gzip 格式的支持
- bz2 — 对 bzip2 压缩算法的支持
- lzma — 用 LZMA 算法压缩
- zipfile — 在 ZIP 归档中工作
- tarfile — Read and write tar archive files
- 文件格式
- csv — CSV 文件读写
- configparser — Configuration file parser
- netrc — netrc file processing
- xdrlib — Encode and decode XDR data
- plistlib — Generate and parse Mac OS X .plist files
- 加密服务
- hashlib — 安全哈希与消息摘要
- hmac — 基于密钥的消息验证
- secrets — Generate secure random numbers for managing secrets
- 通用操作系统服务
- os — 操作系统接口模块
- io — 处理流的核心工具
- time — 时间的访问和转换
- argparse — 命令行选项、参数和子命令解析器
- getopt — C-style parser for command line options
- 模块 logging — Python 的日志记录工具
- logging.config — 日志记录配置
- logging.handlers — Logging handlers
- getpass — 便携式密码输入工具
- curses — 终端字符单元显示的处理
- curses.textpad — Text input widget for curses programs
- curses.ascii — Utilities for ASCII characters
- curses.panel — A panel stack extension for curses
- platform — Access to underlying platform's identifying data
- errno — Standard errno system symbols
- ctypes — Python 的外部函数库
- 并发执行
- threading — 基于线程的并行
- multiprocessing — 基于进程的并行
- concurrent 包
- concurrent.futures — 启动并行任务
- subprocess — 子进程管理
- sched — 事件调度器
- queue — 一个同步的队列类
- _thread — 底层多线程 API
- _dummy_thread — _thread 的替代模块
- dummy_threading — 可直接替代 threading 模块。
- contextvars — Context Variables
- Context Variables
- Manual Context Management
- asyncio support
- 网络和进程间通信
- asyncio — 异步 I/O
- socket — 底层网络接口
- ssl — TLS/SSL wrapper for socket objects
- select — Waiting for I/O completion
- selectors — 高级 I/O 复用库
- asyncore — 异步socket处理器
- asynchat — 异步 socket 指令/响应 处理器
- signal — Set handlers for asynchronous events
- mmap — Memory-mapped file support
- 互联网数据处理
- email — 电子邮件与 MIME 处理包
- json — JSON 编码和解码器
- mailcap — Mailcap file handling
- mailbox — Manipulate mailboxes in various formats
- mimetypes — Map filenames to MIME types
- base64 — Base16, Base32, Base64, Base85 数据编码
- binhex — 对binhex4文件进行编码和解码
- binascii — 二进制和 ASCII 码互转
- quopri — Encode and decode MIME quoted-printable data
- uu — Encode and decode uuencode files
- 结构化标记处理工具
- html — 超文本标记语言支持
- html.parser — 简单的 HTML 和 XHTML 解析器
- html.entities — HTML 一般实体的定义
- XML处理模块
- xml.etree.ElementTree — The ElementTree XML API
- xml.dom — The Document Object Model API
- xml.dom.minidom — Minimal DOM implementation
- xml.dom.pulldom — Support for building partial DOM trees
- xml.sax — Support for SAX2 parsers
- xml.sax.handler — Base classes for SAX handlers
- xml.sax.saxutils — SAX Utilities
- xml.sax.xmlreader — Interface for XML parsers
- xml.parsers.expat — Fast XML parsing using Expat
- 互联网协议和支持
- webbrowser — 方便的Web浏览器控制器
- cgi — Common Gateway Interface support
- cgitb — Traceback manager for CGI scripts
- wsgiref — WSGI Utilities and Reference Implementation
- urllib — URL 处理模块
- urllib.request — 用于打开 URL 的可扩展库
- urllib.response — Response classes used by urllib
- urllib.parse — Parse URLs into components
- urllib.error — Exception classes raised by urllib.request
- urllib.robotparser — Parser for robots.txt
- http — HTTP 模块
- http.client — HTTP协议客户端
- ftplib — FTP protocol client
- poplib — POP3 protocol client
- imaplib — IMAP4 protocol client
- nntplib — NNTP protocol client
- smtplib —SMTP协议客户端
- smtpd — SMTP Server
- telnetlib — Telnet client
- uuid — UUID objects according to RFC 4122
- socketserver — A framework for network servers
- http.server — HTTP 服务器
- http.cookies — HTTP state management
- http.cookiejar — Cookie handling for HTTP clients
- xmlrpc — XMLRPC 服务端与客户端模块
- xmlrpc.client — XML-RPC client access
- xmlrpc.server — Basic XML-RPC servers
- ipaddress — IPv4/IPv6 manipulation library
- 多媒体服务
- audioop — Manipulate raw audio data
- aifc — Read and write AIFF and AIFC files
- sunau — 读写 Sun AU 文件
- wave — 读写WAV格式文件
- chunk — Read IFF chunked data
- colorsys — Conversions between color systems
- imghdr — 推测图像类型
- sndhdr — 推测声音文件的类型
- ossaudiodev — Access to OSS-compatible audio devices
- 国际化
- gettext — 多语种国际化服务
- locale — 国际化服务
- 程序框架
- turtle — 海龟绘图
- cmd — 支持面向行的命令解释器
- shlex — Simple lexical analysis
- Tk图形用户界面(GUI)
- tkinter — Tcl/Tk的Python接口
- tkinter.ttk — Tk themed widgets
- tkinter.tix — Extension widgets for Tk
- tkinter.scrolledtext — 滚动文字控件
- IDLE
- 其他图形用户界面（GUI）包
- 开发工具
- typing — 类型标注支持
- pydoc — Documentation generator and online help system
- doctest — Test interactive Python examples
- unittest — 单元测试框架
- unittest.mock — mock object library
- unittest.mock 上手指南
- 2to3 - 自动将 Python 2 代码转为 Python 3 代码
- test — Regression tests package for Python
- test.support — Utilities for the Python test suite
- test.support.script_helper — Utilities for the Python execution tests
- 调试和分析
- bdb — Debugger framework
- faulthandler — Dump the Python traceback
- pdb — The Python Debugger
- The Python Profilers
- timeit — 测量小代码片段的执行时间
- trace — Trace or track Python statement execution
- tracemalloc — Trace memory allocations
- 软件打包和分发
- distutils — 构建和安装 Python 模块
- ensurepip — Bootstrapping the pip installer
- venv — 创建虚拟环境
- zipapp — Manage executable Python zip archives
- Python运行时服务
- sys — 系统相关的参数和函数
- sysconfig — Provide access to Python's configuration information
- builtins — 内建对象
- main — 顶层脚本环境
- warnings — Warning control
- dataclasses — 数据类
- contextlib — Utilities for with-statement contexts
- abc — 抽象基类
- atexit — 退出处理器
- traceback — Print or retrieve a stack traceback
- future — Future 语句定义
- gc — 垃圾回收器接口
- inspect — 检查对象
- site — Site-specific configuration hook
- 自定义 Python 解释器
- code — Interpreter base classes
- codeop — Compile Python code
- 导入模块
- zipimport — Import modules from Zip archives
- pkgutil — Package extension utility
- modulefinder — 查找脚本使用的模块
- runpy — Locating and executing Python modules
- importlib — The implementation of import
- Python 语言服务
- parser — Access Python parse trees
- ast — 抽象语法树
- symtable — Access to the compiler's symbol tables
- symbol — 与 Python 解析树一起使用的常量
- token — 与Python解析树一起使用的常量
- keyword — 检验Python关键字
- tokenize — Tokenizer for Python source
- tabnanny — 模糊缩进检测
- pyclbr — Python class browser support
- py_compile — Compile Python source files
- compileall — Byte-compile Python libraries
- dis — Python 字节码反汇编器
- pickletools — Tools for pickle developers
- 杂项服务
- formatter — Generic output formatting
- Windows系统相关模块
- msilib — Read and write Microsoft Installer files
- msvcrt — Useful routines from the MS VC++ runtime
- winreg — Windows 注册表访问
- winsound — Sound-playing interface for Windows
- Unix 专有服务
- posix — The most common POSIX system calls
- pwd — 用户密码数据库
- spwd — The shadow password database
- grp — The group database
- crypt — Function to check Unix passwords
- termios — POSIX style tty control
- tty — 终端控制功能
- pty — Pseudo-terminal utilities
- fcntl — The fcntl and ioctl system calls
- pipes — Interface to shell pipelines
- resource — Resource usage information
- nis — Interface to Sun's NIS (Yellow Pages)
- Unix syslog 库例程
- 被取代的模块
- optparse — Parser for command line options
- imp — Access the import internals
- 未创建文档的模块
- 平台特定模块
- 扩展和嵌入 Python 解释器
- 推荐的第三方工具
- 不使用第三方工具创建扩展
- 使用 C 或 C++ 扩展 Python
- 自定义扩展类型：教程
- 定义扩展类型：已分类主题
- 构建C/C++扩展
- 在Windows平台编译C和C++扩展
- 在更大的应用程序中嵌入 CPython 运行时
- Embedding Python in Another Application
- Python/C API 参考手册
- 概述
- 代码标准
- 包含文件
- 有用的宏
- 对象、类型和引用计数
- 异常
- 嵌入Python
- 调试构建
- 稳定的应用程序二进制接口
- The Very High Level Layer
- Reference Counting
- 异常处理
- Printing and clearing
- 抛出异常
- Issuing warnings
- Querying the error indicator
- Signal Handling
- Exception Classes
- Exception Objects
- Unicode Exception Objects
- Recursion Control
- 标准异常
- 标准警告类别
- 工具
- 操作系统实用程序
- 系统功能
- 过程控制
- 导入模块
- Data marshalling support
- 语句解释及变量编译
- 字符串转换与格式化
- 反射
- 编解码器注册与支持功能
- 抽象对象层
- Object Protocol
- 数字协议
- Sequence Protocol
- Mapping Protocol
- 迭代器协议
- 缓冲协议
- Old Buffer Protocol
- 具体的对象层
- 基本对象
- 数值对象
- 序列对象
- 容器对象
- 函数对象
- 其他对象
- Initialization, Finalization, and Threads
- 在Python初始化之前
- 全局配置变量
- Initializing and finalizing the interpreter
- Process-wide parameters
- Thread State and the Global Interpreter Lock
- Sub-interpreter support
- Asynchronous Notifications
- Profiling and Tracing
- Advanced Debugger Support
- Thread Local Storage Support
- 内存管理
- 概述
- 原始内存接口
- Memory Interface
- 对象分配器
- 默认内存分配器
- Customize Memory Allocators
- The pymalloc allocator
- tracemalloc C API
- 示例
- 对象实现支持
- 在堆中分配对象
- Common Object Structures
- Type 对象
- Number Object Structures
- Mapping Object Structures
- Sequence Object Structures
- Buffer Object Structures
- Async Object Structures
- 使对象类型支持循环垃圾回收
- API 和 ABI 版本管理
- 分发 Python 模块
- 关键术语
- 开源许可与协作
- 安装工具
- 阅读指南
- 我该如何...？
- ...为我的项目选择一个名字？
- ...创建和分发二进制扩展？
- 安装 Python 模块
- 关键术语
- 基本使用
- 我应如何 ...？
- ... 在 Python 3.4 之前的 Python 版本中安装 pip ？
- ... 只为当前用户安装软件包？
- ... 安装科学计算类 Python 软件包？
- ... 使用并行安装的多个 Python 版本？
- 常见的安装问题
- 在 Linux 的系统 Python 版本上安装
- 未安装 pip
- 安装二进制编译扩展
- Python 常用指引
- 将 Python 2 代码迁移到 Python 3
- 简要说明
- 详情
- 将扩展模块移植到 Python 3
- 条件编译
- 对象API的更改
- 模块初始化和状态
- CObject 替换为 Capsule
- 其他选项
- Curses Programming with Python
- What is curses?
- Starting and ending a curses application
- Windows and Pads
- Displaying Text
- User Input
- For More Information
- 实现描述器
- 摘要
- 定义和简介
- 描述器协议
- 发起调用描述符
- 描述符示例
- Properties
- 函数和方法
- Static Methods and Class Methods
- 函数式编程指引
- 概述
- 迭代器
- 生成器表达式和列表推导式
- 生成器
- 内置函数
- itertools 模块
- The functools module
- Small functions and the lambda expression
- Revision History and Acknowledgements
- 引用文献
- 日志 HOWTO
- 日志基础教程
- 进阶日志教程
- 日志级别
- 有用的处理程序
- 记录日志中引发的异常
- 使用任意对象作为消息
- 优化
- 日志操作手册
- 在多个模块中使用日志
- 在多线程中使用日志
- 使用多个日志处理器和多种格式化
- 在多个地方记录日志
- 日志服务器配置示例
- 处理日志处理器的阻塞
- Sending and receiving logging events across a network
- Adding contextual information to your logging output
- Logging to a single file from multiple processes
- Using file rotation
- Use of alternative formatting styles
- Customizing LogRecord
- Subclassing QueueHandler - a ZeroMQ example
- Subclassing QueueListener - a ZeroMQ example
- An example dictionary-based configuration
- Using a rotator and namer to customize log rotation processing
- A more elaborate multiprocessing example
- Inserting a BOM into messages sent to a SysLogHandler
- Implementing structured logging
- Customizing handlers with dictConfig()
- Using particular formatting styles throughout your application
- Configuring filters with dictConfig()
- Customized exception formatting
- Speaking logging messages
- Buffering logging messages and outputting them conditionally
- Formatting times using UTC (GMT) via configuration
- Using a context manager for selective logging
- 正则表达式HOWTO
- 概述
- 简单模式
- 使用正则表达式
- 更多模式能力
- 修改字符串
- 常见问题
- 反馈
- 套接字编程指南
- 套接字
- 创建套接字
- 使用一个套接字
- 断开连接
- 非阻塞的套接字
- 排序指南
- 基本排序
- 关键函数
- Operator 模块函数
- 升序和降序
- 排序稳定性和排序复杂度
- 使用装饰-排序-去装饰的旧方法
- 使用 cmp 参数的旧方法
- 其它
- Unicode 指南
- Unicode 概述
- Python's Unicode Support
- Reading and Writing Unicode Data
- Acknowledgements
- 如何使用urllib包获取网络资源
- 概述
- Fetching URLs
- 处理异常
- info and geturl
- Openers and Handlers
- Basic Authentication
- Proxies
- Sockets and Layers
- 脚注
- Argparse 教程
- 概念
- 基础
- 位置参数介绍
- Introducing Optional arguments
- Combining Positional and Optional arguments
- Getting a little more advanced
- Conclusion
- ipaddress模块介绍
- 创建 Address/Network/Interface 对象
- 审查 Address/Network/Interface 对象
- Network 作为 Address 列表
- 比较
- 将IP地址与其他模块一起使用
- 实例创建失败时获取更多详细信息
- Argument Clinic How-To
- The Goals Of Argument Clinic
- Basic Concepts And Usage
- Converting Your First Function
- Advanced Topics
- 使用 DTrace 和 SystemTap 检测CPython
- Enabling the static markers
- Static DTrace probes
- Static SystemTap markers
- Available static markers
- SystemTap Tapsets
- 示例
- Python 常见问题
- Python常见问题
- 一般信息
- 现实世界中的 Python
- 编程常见问题
- 一般问题
- 核心语言
- 数字和字符串
- 性能
- 序列（元组/列表）
- 对象
- 模块
- 设计和历史常见问题
- 为什么Python使用缩进来分组语句？
- 为什么简单的算术运算得到奇怪的结果？
- 为什么浮点计算不准确？
- 为什么Python字符串是不可变的？
- 为什么必须在方法定义和调用中显式使用“self”？
- 为什么不能在表达式中赋值？
- 为什么Python对某些功能（例如list.index()）使用方法来实现，而其他功能（例如len(List)）使用函数实现？
- 为什么 join()是一个字符串方法而不是列表或元组方法？
- 异常有多快？
- 为什么Python中没有switch或case语句？
- 难道不能在解释器中模拟线程，而非得依赖特定于操作系统的线程实现吗？
- 为什么lambda表达式不能包含语句？
- 可以将Python编译为机器代码，C或其他语言吗？
- Python如何管理内存？
- 为什么CPython不使用更传统的垃圾回收方案？
- CPython退出时为什么不释放所有内存？
- 为什么有单独的元组和列表数据类型？
- 列表是如何在CPython中实现的？
- 字典是如何在CPython中实现的？
- 为什么字典key必须是不可变的？
- 为什么 list.sort() 没有返回排序列表？
- 如何在Python中指定和实施接口规范？
- 为什么没有goto？
- 为什么原始字符串（r-strings）不能以反斜杠结尾？
- 为什么Python没有属性赋值的“with”语句？
- 为什么 if/while/def/class语句需要冒号？
- 为什么Python在列表和元组的末尾允许使用逗号？
- 代码库和插件 FAQ
- 通用的代码库问题
- 通用任务
- 线程相关
- 输入输出
- 网络 / Internet 编程
- 数据库
- 数学和数字
- 扩展/嵌入常见问题
- 可以使用C语言中创建自己的函数吗？
- 可以使用C++语言中创建自己的函数吗？
- C很难写，有没有其他选择？
- 如何从C执行任意Python语句？
- 如何从C中评估任意Python表达式？
- 如何从Python对象中提取C的值？
- 如何使用Py_BuildValue()创建任意长度的元组？
- 如何从C调用对象的方法？
- 如何捕获PyErr_Print()（或打印到stdout / stderr的任何内容）的输出？
- 如何从C访问用Python编写的模块？
- 如何从Python接口到C ++对象？
- 我使用Setup文件添加了一个模块，为什么make失败了？
- 如何调试扩展？
- 我想在Linux系统上编译一个Python模块，但是缺少一些文件。为什么?
- 如何区分“输入不完整”和“输入无效”？
- 如何找到未定义的g++符号__builtin_new或__pure_virtual？
- 能否创建一个对象类，其中部分方法在C中实现，而其他方法在Python中实现（例如通过继承）？
- Python在Windows上的常见问题
- 我怎样在Windows下运行一个Python程序？
- 我怎么让 Python 脚本可执行？
- 为什么有时候 Python 程序会启动缓慢？
- 我怎样使用Python脚本制作可执行文件？
- *.pyd 文件和DLL文件相同吗？
- 我怎样将Python嵌入一个Windows程序？
- 如何让编辑器不要在我的 Python 源代码中插入 tab ？
- 如何在不阻塞的情况下检查按键？
- 图形用户界面（GUI）常见问题
- 图形界面常见问题
- Python 是否有平台无关的图形界面工具包？
- 有哪些Python的GUI工具是某个平台专用的？
- 有关Tkinter的问题
- “为什么我的电脑上安装了 Python ？”
- 什么是Python？
- 为什么我的电脑上安装了 Python ？
- 我能删除 Python 吗？
- 术语对照表
- 文档说明
- Python 文档贡献者
- 解决 Bug
- 文档错误
- 使用 Python 的错误追踪系统
- 开始为 Python 贡献您的知识
- 版权
- 历史和许可证
- 软件历史
- 访问Python或以其他方式使用Python的条款和条件
- Python 3.7.3 的 PSF 许可协议
- Python 2.0 的 BeOpen.com 许可协议
- Python 1.6.1 的 CNRI 许可协议
- Python 0.9.0 至 1.2 的 CWI 许可协议
- 集成软件的许可和认可
- Mersenne Twister
- 套接字
- Asynchronous socket services
- Cookie management
- Execution tracing
- UUencode and UUdecode functions
- XML Remote Procedure Calls
- test_epoll
- Select kqueue
- SipHash24
- strtod and dtoa
- OpenSSL
- expat
- libffi
- zlib
- cfuhash
- libmpdec