### 导航 - [索引](../genindex.xhtml "总目录") - [模块](../py-modindex.xhtml "Python 模块索引") | - [下一页](asyncore.xhtml "asyncore --- 异步socket处理器") | - [上一页](select.xhtml "select --- Waiting for I/O completion") | -  - [Python](https://www.python.org/) » - zh\_CN 3.7.3 [文档](../index.xhtml) » - [Python 标准库](index.xhtml) » - [网络和进程间通信](ipc.xhtml) » - $('.inline-search').show(0); | # [`selectors`](#module-selectors "selectors: High-level I/O multiplexing.") --- 高级 I/O 复用库 3\.4 新版功能. **源码:** [Lib/selectors.py](https://github.com/python/cpython/tree/3.7/Lib/selectors.py) \[https://github.com/python/cpython/tree/3.7/Lib/selectors.py\] - - - - - - ## 概述 This module allows high-level and efficient I/O multiplexing, built upon the [`select`](select.xhtml#module-select "select: Wait for I/O completion on multiple streams.") module primitives. Users are encouraged to use this module instead, unless they want precise control over the OS-level primitives used. It defines a [`BaseSelector`](#selectors.BaseSelector "selectors.BaseSelector") abstract base class, along with several concrete implementations ([`KqueueSelector`](#selectors.KqueueSelector "selectors.KqueueSelector"), [`EpollSelector`](#selectors.EpollSelector "selectors.EpollSelector")...), that can be used to wait for I/O readiness notification on multiple file objects. In the following, "file object" refers to any object with a `fileno()` method, or a raw file descriptor. See [file object](../glossary.xhtml#term-file-object). [`DefaultSelector`](#selectors.DefaultSelector "selectors.DefaultSelector") is an alias to the most efficient implementation available on the current platform: this should be the default choice for most users. 注解 The type of file objects supported depends on the platform: on Windows, sockets are supported, but not pipes, whereas on Unix, both are supported (some other types may be supported as well, such as fifos or special file devices). 参见 [`select`](select.xhtml#module-select "select: Wait for I/O completion on multiple streams.")Low-level I/O multiplexing module. ## 类 Classes hierarchy: ``` BaseSelector +-- SelectSelector +-- PollSelector +-- EpollSelector +-- DevpollSelector +-- KqueueSelector ``` In the following, *events* is a bitwise mask indicating which I/O events should be waited for on a given file object. It can be a combination of the modules constants below: > 常数 > > 意义 > > `EVENT_READ` > > Available for read > > `EVENT_WRITE` > > Available for write *class* `selectors.``SelectorKey`A [`SelectorKey`](#selectors.SelectorKey "selectors.SelectorKey") is a [`namedtuple`](collections.xhtml#collections.namedtuple "collections.namedtuple") used to associate a file object to its underlying file descriptor, selected event mask and attached data. It is returned by several [`BaseSelector`](#selectors.BaseSelector "selectors.BaseSelector")methods. `fileobj`File object registered. `fd`Underlying file descriptor. `events`Events that must be waited for on this file object. `data`Optional opaque data associated to this file object: for example, this could be used to store a per-client session ID. *class* `selectors.``BaseSelector`A [`BaseSelector`](#selectors.BaseSelector "selectors.BaseSelector") is used to wait for I/O event readiness on multiple file objects. It supports file stream registration, unregistration, and a method to wait for I/O events on those streams, with an optional timeout. It's an abstract base class, so cannot be instantiated. Use [`DefaultSelector`](#selectors.DefaultSelector "selectors.DefaultSelector") instead, or one of [`SelectSelector`](#selectors.SelectSelector "selectors.SelectSelector"), [`KqueueSelector`](#selectors.KqueueSelector "selectors.KqueueSelector") etc. if you want to specifically use an implementation, and your platform supports it. [`BaseSelector`](#selectors.BaseSelector "selectors.BaseSelector") and its concrete implementations support the [context manager](../glossary.xhtml#term-context-manager) protocol. *abstractmethod* `register`(*fileobj*, *events*, *data=None*)Register a file object for selection, monitoring it for I/O events. *fileobj* is the file object to monitor. It may either be an integer file descriptor or an object with a `fileno()` method. *events* is a bitwise mask of events to monitor. *data* is an opaque object. This returns a new [`SelectorKey`](#selectors.SelectorKey "selectors.SelectorKey") instance, or raises a [`ValueError`](exceptions.xhtml#ValueError "ValueError") in case of invalid event mask or file descriptor, or [`KeyError`](exceptions.xhtml#KeyError "KeyError") if the file object is already registered. *abstractmethod* `unregister`(*fileobj*)Unregister a file object from selection, removing it from monitoring. A file object shall be unregistered prior to being closed. *fileobj* must be a file object previously registered. This returns the associated [`SelectorKey`](#selectors.SelectorKey "selectors.SelectorKey") instance, or raises a [`KeyError`](exceptions.xhtml#KeyError "KeyError") if *fileobj* is not registered. It will raise [`ValueError`](exceptions.xhtml#ValueError "ValueError") if *fileobj* is invalid (e.g. it has no `fileno()`method or its `fileno()` method has an invalid return value). `modify`(*fileobj*, *events*, *data=None*)Change a registered file object's monitored events or attached data. This is equivalent to `BaseSelector.unregister(fileobj)()` followed by `BaseSelector.register(fileobj, events, data)()`, except that it can be implemented more efficiently. This returns a new [`SelectorKey`](#selectors.SelectorKey "selectors.SelectorKey") instance, or raises a [`ValueError`](exceptions.xhtml#ValueError "ValueError") in case of invalid event mask or file descriptor, or [`KeyError`](exceptions.xhtml#KeyError "KeyError") if the file object is not registered. *abstractmethod* `select`(*timeout=None*)Wait until some registered file objects become ready, or the timeout expires. If `timeout > 0`, this specifies the maximum wait time, in seconds. If `timeout <= 0`, the call won't block, and will report the currently ready file objects. If *timeout* is `None`, the call will block until a monitored file object becomes ready. This returns a list of `(key, events)` tuples, one for each ready file object. *key* is the [`SelectorKey`](#selectors.SelectorKey "selectors.SelectorKey") instance corresponding to a ready file object. *events* is a bitmask of events ready on this file object. 注解 This method can return before any file object becomes ready or the timeout has elapsed if the current process receives a signal: in this case, an empty list will be returned. 在 3.5 版更改: The selector is now retried with a recomputed timeout when interrupted by a signal if the signal handler did not raise an exception (see [**PEP 475**](https://www.python.org/dev/peps/pep-0475) \[https://www.python.org/dev/peps/pep-0475\] for the rationale), instead of returning an empty list of events before the timeout. `close`()Close the selector. This must be called to make sure that any underlying resource is freed. The selector shall not be used once it has been closed. `get_key`(*fileobj*)Return the key associated with a registered file object. This returns the [`SelectorKey`](#selectors.SelectorKey "selectors.SelectorKey") instance associated to this file object, or raises [`KeyError`](exceptions.xhtml#KeyError "KeyError") if the file object is not registered. *abstractmethod* `get_map`()Return a mapping of file objects to selector keys. This returns a [`Mapping`](collections.abc.xhtml#collections.abc.Mapping "collections.abc.Mapping") instance mapping registered file objects to their associated [`SelectorKey`](#selectors.SelectorKey "selectors.SelectorKey")instance. *class* `selectors.``DefaultSelector`The default selector class, using the most efficient implementation available on the current platform. This should be the default choice for most users. *class* `selectors.``SelectSelector`[`select.select()`](select.xhtml#select.select "select.select")-based selector. *class* `selectors.``PollSelector`[`select.poll()`](select.xhtml#select.poll "select.poll")-based selector. *class* `selectors.``EpollSelector`[`select.epoll()`](select.xhtml#select.epoll "select.epoll")-based selector. `fileno`()This returns the file descriptor used by the underlying [`select.epoll()`](select.xhtml#select.epoll "select.epoll") object. *class* `selectors.``DevpollSelector`[`select.devpoll()`](select.xhtml#select.devpoll "select.devpoll")-based selector. `fileno`()This returns the file descriptor used by the underlying [`select.devpoll()`](select.xhtml#select.devpoll "select.devpoll") object. 3\.5 新版功能. *class* `selectors.``KqueueSelector`[`select.kqueue()`](select.xhtml#select.kqueue "select.kqueue")-based selector. `fileno`()This returns the file descriptor used by the underlying [`select.kqueue()`](select.xhtml#select.kqueue "select.kqueue") object. ## 示例 Here is a simple echo server implementation: ``` import selectors import socket sel = selectors.DefaultSelector() def accept(sock, mask): conn, addr = sock.accept() # Should be ready print('accepted', conn, 'from', addr) conn.setblocking(False) sel.register(conn, selectors.EVENT_READ, read) def read(conn, mask): data = conn.recv(1000) # Should be ready if data: print('echoing', repr(data), 'to', conn) conn.send(data) # Hope it won't block else: print('closing', conn) sel.unregister(conn) conn.close() sock = socket.socket() sock.bind(('localhost', 1234)) sock.listen(100) sock.setblocking(False) sel.register(sock, selectors.EVENT_READ, accept) while True: events = sel.select() for key, mask in events: callback = key.data callback(key.fileobj, mask) ``` ### 导航 - [索引](../genindex.xhtml "总目录") - [模块](../py-modindex.xhtml "Python 模块索引") | - [下一页](asyncore.xhtml "asyncore --- 异步socket处理器") | - [上一页](select.xhtml "select --- Waiting for I/O completion") | -  - [Python](https://www.python.org/) » - zh\_CN 3.7.3 [文档](../index.xhtml) » - [Python 标准库](index.xhtml) » - [网络和进程间通信](ipc.xhtml) » - $('.inline-search').show(0); | © [版权所有](../copyright.xhtml) 2001-2019, Python Software Foundation. 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