### 导航 - [索引](../genindex.xhtml "总目录") - [模块](../py-modindex.xhtml "Python 模块索引") | - [下一页](zipapp.xhtml "zipapp --- Manage executable Python zip archives") | - [上一页](ensurepip.xhtml "ensurepip --- Bootstrapping the pip installer") | -  - [Python](https://www.python.org/) » - zh\_CN 3.7.3 [文档](../index.xhtml) » - [Python 标准库](index.xhtml) » - [软件打包和分发](distribution.xhtml) » - $('.inline-search').show(0); | # [`venv`](#module-venv "venv: Creation of virtual environments.") --- 创建虚拟环境 3\.3 新版功能. **源码：** [Lib/venv/](https://github.com/python/cpython/tree/3.7/Lib/venv/) \[https://github.com/python/cpython/tree/3.7/Lib/venv/\] - - - - - - [`venv`](#module-venv "venv: Creation of virtual environments.") 模块支持使用自己的站点目录创建轻量级“虚拟环境”，可选择与系统站点目录隔离。每个虚拟环境都有自己的 Python 二进制文件（与用于创建此环境的二进制文件的版本相匹配），并且可以在其站点目录中拥有自己独立的已安装 Python 软件包集。 有关 Python 虚拟环境的更多信息，请参阅 [**PEP 405**](https://www.python.org/dev/peps/pep-0405) \[https://www.python.org/dev/peps/pep-0405\] 。 参见 [Python 打包用户指南：创建和使用虚拟环境](https://packaging.python.org/installing/#creating-virtual-environments) \[https://packaging.python.org/installing/#creating-virtual-environments\] 注解 从 Python 3.6 开始，不推荐使用 `pyvenv` 脚本，而是使用 `python3 -m venv` 来帮助防止任何关于虚拟环境将基于哪个 Python 解释器的混淆。 ## 创建虚拟环境 通过执行 `venv` 指令来创建一个 [虚拟环境](#venv-def): ``` python3 -m venv /path/to/new/virtual/environment ``` Running this command creates the target directory (creating any parent directories that don't exist already) and places a `pyvenv.cfg` file in it with a `home` key pointing to the Python installation from which the command was run. It also creates a `bin` (or `Scripts` on Windows) subdirectory containing a copy/symlink of the Python binary/binaries (as appropriate for the platform or arguments used at environment creation time). It also creates an (initially empty) `lib/pythonX.Y/site-packages` subdirectory (on Windows, this is `Lib\site-packages`). If an existing directory is specified, it will be re-used. 3\.6 版后已移除: `pyvenv` 是 Python 3.3 和 3.4 中创建虚拟环境的推荐工具，不过 [在 Python 3.6 中已弃用](https://docs.python.org/dev/whatsnew/3.6.html#deprecated-features) \[https://docs.python.org/dev/whatsnew/3.6.html#deprecated-features\]。 在 3.5 版更改: 现在推荐使用 `venv` 来创建虚拟环境。 On Windows, invoke the `venv` command as follows: ``` c:\>c:\Python35\python -m venv c:\path\to\myenv ``` Alternatively, if you configured the `PATH` and `PATHEXT` variables for your [Python installation](../using/windows.xhtml#using-on-windows): ``` c:\>python -m venv c:\path\to\myenv ``` The command, if run with `-h`, will show the available options: ``` usage: venv [-h] [--system-site-packages] [--symlinks | --copies] [--clear] [--upgrade] [--without-pip] [--prompt PROMPT] ENV_DIR [ENV_DIR ...] Creates virtual Python environments in one or more target directories. positional arguments: ENV_DIR A directory to create the environment in. optional arguments: -h, --help show this help message and exit --system-site-packages Give the virtual environment access to the system site-packages dir. --symlinks Try to use symlinks rather than copies, when symlinks are not the default for the platform. --copies Try to use copies rather than symlinks, even when symlinks are the default for the platform. --clear Delete the contents of the environment directory if it already exists, before environment creation. --upgrade Upgrade the environment directory to use this version of Python, assuming Python has been upgraded in-place. --without-pip Skips installing or upgrading pip in the virtual environment (pip is bootstrapped by default) --prompt PROMPT Provides an alternative prompt prefix for this environment. Once an environment has been created, you may wish to activate it, e.g. by sourcing an activate script in its bin directory. ``` 在 3.4 版更改: Installs pip by default, added the `--without-pip` and `--copies`options 在 3.4 版更改: In earlier versions, if the target directory already existed, an error was raised, unless the `--clear` or `--upgrade` option was provided. 注解 While symlinks are supported on Windows, they are not recommended. Of particular note is that double-clicking `python.exe` in File Explorer will resolve the symlink eagerly and ignore the virtual environment. The created `pyvenv.cfg` file also includes the `include-system-site-packages` key, set to `true` if `venv` is run with the `--system-site-packages` option, `false` otherwise. Unless the `--without-pip` option is given, [`ensurepip`](ensurepip.xhtml#module-ensurepip "ensurepip: Bootstrapping the "pip" installer into an existing Python installation or virtual environment.") will be invoked to bootstrap `pip` into the virtual environment. Multiple paths can be given to `venv`, in which case an identical virtual environment will be created, according to the given options, at each provided path. Once a virtual environment has been created, it can be "activated" using a script in the virtual environment's binary directory. The invocation of the script is platform-specific (<venv> must be replaced by the path of the directory containing the virtual environment): 平台 Shell 用于激活虚拟环境的命令 Posix bash/zsh $ source <venv>/bin/activate fish $ . <venv>/bin/activate.fish csh/tcsh $ source <venv>/bin/activate.csh Windows cmd.exe C:\\> <venv>\\Scripts\\activate.bat PowerShell PS C:\\> <venv>\\Scripts\\Activate.ps1 You don't specifically *need* to activate an environment; activation just prepends the virtual environment's binary directory to your path, so that "python" invokes the virtual environment's Python interpreter and you can run installed scripts without having to use their full path. However, all scripts installed in a virtual environment should be runnable without activating it, and run with the virtual environment's Python automatically. You can deactivate a virtual environment by typing "deactivate" in your shell. The exact mechanism is platform-specific: for example, the Bash activation script defines a "deactivate" function, whereas on Windows there are separate scripts called `deactivate.bat` and `Deactivate.ps1` which are installed when the virtual environment is created. 3\.4 新版功能: `fish` and `csh` activation scripts. 注解 A virtual environment is a Python environment such that the Python interpreter, libraries and scripts installed into it are isolated from those installed in other virtual environments, and (by default) any libraries installed in a "system" Python, i.e., one which is installed as part of your operating system. A virtual environment is a directory tree which contains Python executable files and other files which indicate that it is a virtual environment. Common installation tools such as `Setuptools` and `pip` work as expected with virtual environments. In other words, when a virtual environment is active, they install Python packages into the virtual environment without needing to be told to do so explicitly. When a virtual environment is active (i.e., the virtual environment's Python interpreter is running), the attributes [`sys.prefix`](sys.xhtml#sys.prefix "sys.prefix") and [`sys.exec_prefix`](sys.xhtml#sys.exec_prefix "sys.exec_prefix") point to the base directory of the virtual environment, whereas [`sys.base_prefix`](sys.xhtml#sys.base_prefix "sys.base_prefix") and [`sys.base_exec_prefix`](sys.xhtml#sys.base_exec_prefix "sys.base_exec_prefix") point to the non-virtual environment Python installation which was used to create the virtual environment. If a virtual environment is not active, then [`sys.prefix`](sys.xhtml#sys.prefix "sys.prefix") is the same as [`sys.base_prefix`](sys.xhtml#sys.base_prefix "sys.base_prefix") and [`sys.exec_prefix`](sys.xhtml#sys.exec_prefix "sys.exec_prefix") is the same as [`sys.base_exec_prefix`](sys.xhtml#sys.base_exec_prefix "sys.base_exec_prefix") (they all point to a non-virtual environment Python installation). When a virtual environment is active, any options that change the installation path will be ignored from all distutils configuration files to prevent projects being inadvertently installed outside of the virtual environment. When working in a command shell, users can make a virtual environment active by running an `activate` script in the virtual environment's executables directory (the precise filename is shell-dependent), which prepends the virtual environment's directory for executables to the `PATH` environment variable for the running shell. There should be no need in other circumstances to activate a virtual environment—scripts installed into virtual environments have a "shebang" line which points to the virtual environment's Python interpreter. This means that the script will run with that interpreter regardless of the value of `PATH`. On Windows, "shebang" line processing is supported if you have the Python Launcher for Windows installed (this was added to Python in 3.3 - see [**PEP 397**](https://www.python.org/dev/peps/pep-0397) \[https://www.python.org/dev/peps/pep-0397\] for more details). Thus, double-clicking an installed script in a Windows Explorer window should run the script with the correct interpreter without there needing to be any reference to its virtual environment in `PATH`. ## API The high-level method described above makes use of a simple API which provides mechanisms for third-party virtual environment creators to customize environment creation according to their needs, the [`EnvBuilder`](#venv.EnvBuilder "venv.EnvBuilder") class. *class* `venv.``EnvBuilder`(*system\_site\_packages=False*, *clear=False*, *symlinks=False*, *upgrade=False*, *with\_pip=False*, *prompt=None*)The [`EnvBuilder`](#venv.EnvBuilder "venv.EnvBuilder") class accepts the following keyword arguments on instantiation: - `system_site_packages` -- a Boolean value indicating that the system Python site-packages should be available to the environment (defaults to `False`). - `clear` -- a Boolean value which, if true, will delete the contents of any existing target directory, before creating the environment. - `symlinks` -- a Boolean value indicating whether to attempt to symlink the Python binary rather than copying. - `upgrade` -- a Boolean value which, if true, will upgrade an existing environment with the running Python - for use when that Python has been upgraded in-place (defaults to `False`). - `with_pip` -- a Boolean value which, if true, ensures pip is installed in the virtual environment. This uses [`ensurepip`](ensurepip.xhtml#module-ensurepip "ensurepip: Bootstrapping the "pip" installer into an existing Python installation or virtual environment.") with the `--default-pip` option. - `prompt` -- a String to be used after virtual environment is activated (defaults to `None` which means directory name of the environment would be used). 在 3.4 版更改: Added the `with_pip` parameter 3\.6 新版功能: Added the `prompt` parameter Creators of third-party virtual environment tools will be free to use the provided `EnvBuilder` class as a base class. The returned env-builder is an object which has a method, `create`: `create`(*env\_dir*)This method takes as required argument the path (absolute or relative to the current directory) of the target directory which is to contain the virtual environment. The `create` method will either create the environment in the specified directory, or raise an appropriate exception. The `create` method of the `EnvBuilder` class illustrates the hooks available for subclass customization: ``` def create(self, env_dir): """ Create a virtualized Python environment in a directory. env_dir is the target directory to create an environment in. """ env_dir = os.path.abspath(env_dir) context = self.ensure_directories(env_dir) self.create_configuration(context) self.setup_python(context) self.setup_scripts(context) self.post_setup(context) ``` Each of the methods [`ensure_directories()`](#venv.EnvBuilder.ensure_directories "venv.EnvBuilder.ensure_directories"), [`create_configuration()`](#venv.EnvBuilder.create_configuration "venv.EnvBuilder.create_configuration"), [`setup_python()`](#venv.EnvBuilder.setup_python "venv.EnvBuilder.setup_python"), [`setup_scripts()`](#venv.EnvBuilder.setup_scripts "venv.EnvBuilder.setup_scripts") and [`post_setup()`](#venv.EnvBuilder.post_setup "venv.EnvBuilder.post_setup") can be overridden. `ensure_directories`(*env\_dir*)Creates the environment directory and all necessary directories, and returns a context object. This is just a holder for attributes (such as paths), for use by the other methods. The directories are allowed to exist already, as long as either `clear` or `upgrade` were specified to allow operating on an existing environment directory. `create_configuration`(*context*)Creates the `pyvenv.cfg` configuration file in the environment. `setup_python`(*context*)Creates a copy or symlink to the Python executable in the environment. On POSIX systems, if a specific executable `python3.x` was used, symlinks to `python` and `python3` will be created pointing to that executable, unless files with those names already exist. `setup_scripts`(*context*)Installs activation scripts appropriate to the platform into the virtual environment. `post_setup`(*context*)A placeholder method which can be overridden in third party implementations to pre-install packages in the virtual environment or perform other post-creation steps. 在 3.7.2 版更改: Windows now uses redirector scripts for `python[w].exe` instead of copying the actual binaries. In 3.7.2 only [`setup_python()`](#venv.EnvBuilder.setup_python "venv.EnvBuilder.setup_python") does nothing unless running from a build in the source tree. 在 3.7.3 版更改: Windows copies the redirector scripts as part of [`setup_python()`](#venv.EnvBuilder.setup_python "venv.EnvBuilder.setup_python")instead of [`setup_scripts()`](#venv.EnvBuilder.setup_scripts "venv.EnvBuilder.setup_scripts"). This was not the case in 3.7.2. When using symlinks, the original executables will be linked. In addition, [`EnvBuilder`](#venv.EnvBuilder "venv.EnvBuilder") provides this utility method that can be called from [`setup_scripts()`](#venv.EnvBuilder.setup_scripts "venv.EnvBuilder.setup_scripts") or [`post_setup()`](#venv.EnvBuilder.post_setup "venv.EnvBuilder.post_setup") in subclasses to assist in installing custom scripts into the virtual environment. `install_scripts`(*context*, *path*)*path* is the path to a directory that should contain subdirectories "common", "posix", "nt", each containing scripts destined for the bin directory in the environment. The contents of "common" and the directory corresponding to [`os.name`](os.xhtml#os.name "os.name") are copied after some text replacement of placeholders: - `__VENV_DIR__` is replaced with the absolute path of the environment directory. - `__VENV_NAME__` is replaced with the environment name (final path segment of environment directory). - `__VENV_PROMPT__` is replaced with the prompt (the environment name surrounded by parentheses and with a following space) - `__VENV_BIN_NAME__` is replaced with the name of the bin directory (either `bin` or `Scripts`). - `__VENV_PYTHON__` is replaced with the absolute path of the environment's executable. The directories are allowed to exist (for when an existing environment is being upgraded). 有一个方便实用的模块级别的函数: `venv.``create`(*env\_dir*, *system\_site\_packages=False*, *clear=False*, *symlinks=False*, *with\_pip=False*, *prompt=None*)通过关键词参数来创建一个 [`EnvBuilder`](#venv.EnvBuilder "venv.EnvBuilder")，并且使用 *env\_dir* 参数来调用它的 [`create()`](#venv.EnvBuilder.create "venv.EnvBuilder.create") 方法。 3\.3 新版功能. 在 3.4 版更改: Added the `with_pip` parameter 在 3.6 版更改: Added the `prompt` parameter ## 一个扩展 `EnvBuilder` 的例子 下面的脚本展示了如何通过实现一个子类来扩展 [`EnvBuilder`](#venv.EnvBuilder "venv.EnvBuilder")。这个子类会安装 setuptotols 和 pip 的到被创建的虚拟环境中。 ``` import os import os.path from subprocess import Popen, PIPE import sys from threading import Thread from urllib.parse import urlparse from urllib.request import urlretrieve import venv class ExtendedEnvBuilder(venv.EnvBuilder): """ This builder installs setuptools and pip so that you can pip or easy_install other packages into the created virtual environment. :param nodist: If True, setuptools and pip are not installed into the created virtual environment. :param nopip: If True, pip is not installed into the created virtual environment. :param progress: If setuptools or pip are installed, the progress of the installation can be monitored by passing a progress callable. If specified, it is called with two arguments: a string indicating some progress, and a context indicating where the string is coming from. The context argument can have one of three values: 'main', indicating that it is called from virtualize() itself, and 'stdout' and 'stderr', which are obtained by reading lines from the output streams of a subprocess which is used to install the app. If a callable is not specified, default progress information is output to sys.stderr. """ def __init__(self, *args, **kwargs): self.nodist = kwargs.pop('nodist', False) self.nopip = kwargs.pop('nopip', False) self.progress = kwargs.pop('progress', None) self.verbose = kwargs.pop('verbose', False) super().__init__(*args, **kwargs) def post_setup(self, context): """ Set up any packages which need to be pre-installed into the virtual environment being created. :param context: The information for the virtual environment creation request being processed. """ os.environ['VIRTUAL_ENV'] = context.env_dir if not self.nodist: self.install_setuptools(context) # Can't install pip without setuptools if not self.nopip and not self.nodist: self.install_pip(context) def reader(self, stream, context): """ Read lines from a subprocess' output stream and either pass to a progress callable (if specified) or write progress information to sys.stderr. """ progress = self.progress while True: s = stream.readline() if not s: break if progress is not None: progress(s, context) else: if not self.verbose: sys.stderr.write('.') else: sys.stderr.write(s.decode('utf-8')) sys.stderr.flush() stream.close() def install_script(self, context, name, url): _, _, path, _, _, _ = urlparse(url) fn = os.path.split(path)[-1] binpath = context.bin_path distpath = os.path.join(binpath, fn) # Download script into the virtual environment's binaries folder urlretrieve(url, distpath) progress = self.progress if self.verbose: term = '\n' else: term = '' if progress is not None: progress('Installing %s ...%s' % (name, term), 'main') else: sys.stderr.write('Installing %s ...%s' % (name, term)) sys.stderr.flush() # Install in the virtual environment args = [context.env_exe, fn] p = Popen(args, stdout=PIPE, stderr=PIPE, cwd=binpath) t1 = Thread(target=self.reader, args=(p.stdout, 'stdout')) t1.start() t2 = Thread(target=self.reader, args=(p.stderr, 'stderr')) t2.start() p.wait() t1.join() t2.join() if progress is not None: progress('done.', 'main') else: sys.stderr.write('done.\n') # Clean up - no longer needed os.unlink(distpath) def install_setuptools(self, context): """ Install setuptools in the virtual environment. :param context: The information for the virtual environment creation request being processed. """ url = 'https://bitbucket.org/pypa/setuptools/downloads/ez_setup.py' self.install_script(context, 'setuptools', url) # clear up the setuptools archive which gets downloaded pred = lambda o: o.startswith('setuptools-') and o.endswith('.tar.gz') files = filter(pred, os.listdir(context.bin_path)) for f in files: f = os.path.join(context.bin_path, f) os.unlink(f) def install_pip(self, context): """ Install pip in the virtual environment. :param context: The information for the virtual environment creation request being processed. """ url = 'https://raw.github.com/pypa/pip/master/contrib/get-pip.py' self.install_script(context, 'pip', url) def main(args=None): compatible = True if sys.version_info < (3, 3): compatible = False elif not hasattr(sys, 'base_prefix'): compatible = False if not compatible: raise ValueError('This script is only for use with ' 'Python 3.3 or later') else: import argparse parser = argparse.ArgumentParser(prog=__name__, description='Creates virtual Python ' 'environments in one or ' 'more target ' 'directories.') parser.add_argument('dirs', metavar='ENV_DIR', nargs='+', help='A directory in which to create the 'virtual environment.') parser.add_argument('--no-setuptools', default=False, action='store_true', dest='nodist', help="Don't install setuptools or pip in the " "virtual environment.") parser.add_argument('--no-pip', default=False, action='store_true', dest='nopip', help="Don't install pip in the virtual " "environment.") parser.add_argument('--system-site-packages', default=False, action='store_true', dest='system_site', help='Give the virtual environment access to the ' 'system site-packages dir.') if os.name == 'nt': use_symlinks = False else: use_symlinks = True parser.add_argument('--symlinks', default=use_symlinks, action='store_true', dest='symlinks', help='Try to use symlinks rather than copies, ' 'when symlinks are not the default for ' 'the platform.') parser.add_argument('--clear', default=False, action='store_true', dest='clear', help='Delete the contents of the ' 'virtual environment ' 'directory if it already ' 'exists, before virtual ' 'environment creation.') parser.add_argument('--upgrade', default=False, action='store_true', dest='upgrade', help='Upgrade the virtual ' 'environment directory to ' 'use this version of ' 'Python, assuming Python ' 'has been upgraded ' 'in-place.') parser.add_argument('--verbose', default=False, action='store_true', dest='verbose', help='Display the output ' 'from the scripts which ' 'install setuptools and pip.') options = parser.parse_args(args) if options.upgrade and options.clear: raise ValueError('you cannot supply --upgrade and --clear together.') builder = ExtendedEnvBuilder(system_site_packages=options.system_site, clear=options.clear, symlinks=options.symlinks, upgrade=options.upgrade, nodist=options.nodist, nopip=options.nopip, verbose=options.verbose) for d in options.dirs: builder.create(d) if __name__ == '__main__': rc = 1 try: main() rc = 0 except Exception as e: print('Error: %s' % e, file=sys.stderr) sys.exit(rc) ``` 这个脚本同样可以 [在线下载](https://gist.github.com/vsajip/4673395) \[https://gist.github.com/vsajip/4673395\]。 ### 导航 - [索引](../genindex.xhtml "总目录") - [模块](../py-modindex.xhtml "Python 模块索引") | - [下一页](zipapp.xhtml "zipapp --- Manage executable Python zip archives") | - [上一页](ensurepip.xhtml "ensurepip --- Bootstrapping the pip installer") | -  - [Python](https://www.python.org/) » - zh\_CN 3.7.3 [文档](../index.xhtml) » - [Python 标准库](index.xhtml) » - [软件打包和分发](distribution.xhtml) » - $('.inline-search').show(0); | © [版权所有](../copyright.xhtml) 2001-2019, Python Software Foundation. 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