18.5.1. 基事件循环 ¶

The event loop is the central execution device provided by asyncio . It provides multiple facilities, including:

Registering, executing and cancelling delayed calls (timeouts).
Creating client and server 传输 for various kinds of communication.
Launching subprocesses and the associated 传输 for communication with an external program.
Delegating costly function calls to a pool of threads.

class asyncio. BaseEventLoop ¶

18.5.1.1. 运行事件循环 ¶

BaseEventLoop. run_forever ( ) ¶

BaseEventLoop. run_until_complete ( future ) ¶

BaseEventLoop. is_running ( ) ¶

BaseEventLoop. stop ( ) ¶

BaseEventLoop. is_closed ( ) ¶

BaseEventLoop. close ( ) ¶

18.5.1.2. 调用 ¶

Most asyncio functions don’t accept keywords. If you want to pass keywords to your callback, use functools.partial() 。例如， loop.call_soon(functools.partial(print, "Hello", flush=True)) 将调用 print("Hello", flush=True) .

注意

functools.partial() is better than lambda functions, because asyncio can inspect functools.partial() object to display parameters in debug mode, whereas lambda functions have a poor representation.

BaseEventLoop. call_soon ( callback , *args ) ¶

BaseEventLoop. call_soon_threadsafe ( callback , *args ) ¶

18.5.1.3. 延迟调用 ¶

The event loop has its own internal clock for computing timeouts. Which clock is used depends on the (platform-specific) event loop implementation; ideally it is a monotonic clock. This will generally be a different clock than time.time() .

注意

Timeouts (relative delay or absolute 当 ) should not exceed one day.

BaseEventLoop. call_later ( delay , callback , *args ) ¶

BaseEventLoop. call_at ( 当 , callback , *args ) ¶

BaseEventLoop. time ( ) ¶

另请参阅

The asyncio.sleep() 函数。

18.5.1.4. Tasks ¶

BaseEventLoop. create_task ( coro ) ¶

BaseEventLoop. set_task_factory ( factory ) ¶

BaseEventLoop. get_task_factory ( ) ¶

18.5.1.5. Creating connections ¶

协程 BaseEventLoop. create_connection ( protocol_factory , host=None , port=None , * , ssl=None , family=0 , proto=0 , flags=0 , sock=None , local_addr=None , server_hostname=None ) ¶

协程 BaseEventLoop. create_datagram_endpoint ( protocol_factory , local_addr=None , remote_addr=None , * , family=0 , proto=0 , flags=0 , reuse_address=None , reuse_port=None , allow_broadcast=None , sock=None ) ¶

协程 BaseEventLoop. create_unix_connection ( protocol_factory , path , * , ssl=None , sock=None , server_hostname=None ) ¶

18.5.1.6. Creating listening connections ¶

协程 BaseEventLoop. create_server ( protocol_factory , host=None , port=None , * , family=socket.AF_UNSPEC , flags=socket.AI_PASSIVE , sock=None , backlog=100 , ssl=None , reuse_address=None , reuse_port=None ) ¶

协程 BaseEventLoop. create_unix_server ( protocol_factory , path=None , * , sock=None , backlog=100 , ssl=None ) ¶

18.5.1.7. Watch file descriptors ¶

在 Windows 采用 SelectorEventLoop , only socket handles are supported (ex: pipe file descriptors are not supported).

在 Windows 采用 ProactorEventLoop , these methods are not supported.

BaseEventLoop. add_reader ( fd , callback , *args ) ¶

BaseEventLoop. remove_reader ( fd ) ¶

BaseEventLoop. add_writer ( fd , callback , *args ) ¶

BaseEventLoop. remove_writer ( fd ) ¶

The 为读取事件看守文件描述符范例使用低级 BaseEventLoop.add_reader() method to register the file descriptor of a socket.

18.5.1.8. Low-level socket operations ¶

协程 BaseEventLoop. sock_recv ( sock , nbytes ) ¶

从套接字接收数据。返回值是表示收到数据的字节对象。一次接收的最大数据量的指定通过 nbytes .

采用 SelectorEventLoop event loop, the socket sock must be non-blocking.

此方法是协程 .

另请参阅

The socket.socket.recv() 方法。

协程 BaseEventLoop. sock_sendall ( sock , data ) ¶

Send data to the socket. The socket must be connected to a remote socket. This method continues to send data from data until either all data has been sent or an error occurs. None is returned on success. On error, an exception is raised, and there is no way to determine how much data, if any, was successfully processed by the receiving end of the connection.

采用 SelectorEventLoop event loop, the socket sock must be non-blocking.

此方法是协程 .

另请参阅

The socket.socket.sendall() 方法。

协程 BaseEventLoop. sock_connect ( sock , address ) ¶

连接到远程套接字在 address .

The address must be already resolved to avoid the trap of hanging the entire event loop when the address requires doing a DNS lookup. For example, it must be an IP address, not an hostname, for AF_INET and AF_INET6 address families. Use getaddrinfo() to resolve the hostname asynchronously.

采用 SelectorEventLoop event loop, the socket sock must be non-blocking.

此方法是协程 .

另请参阅

The BaseEventLoop.create_connection() method, the open_connection() 函数和 socket.socket.connect() 方法。

协程 BaseEventLoop. sock_accept ( sock ) ¶

接受连接。必须将套接字绑定到地址并监听连接。返回值是一对 (conn, address) where conn 是 new 套接字对象用于发送和接收数据当连接上时，和 address 是绑定到连接另一端的套接字地址。

The socket sock must be non-blocking.

此方法是协程 .

另请参阅

The BaseEventLoop.create_server() method, the start_server() 函数和 socket.socket.accept() 方法。

18.5.1.9. Resolve host name ¶

协程 BaseEventLoop. getaddrinfo ( host , port , * , family=0 , type=0 , proto=0 , flags=0 ) ¶: 此方法是协程，类似 socket.getaddrinfo() 函数但非阻塞。

协程 BaseEventLoop. getnameinfo ( sockaddr , flags=0 ) ¶: 此方法是协程，类似 socket.getnameinfo() 函数但非阻塞。

18.5.1.10. Connect pipes ¶

在 Windows 采用 SelectorEventLoop , these methods are not supported. Use ProactorEventLoop to support pipes on Windows.

协程 BaseEventLoop. connect_read_pipe ( protocol_factory , pipe ) ¶

protocol_factory should instantiate object with Protocol 接口。 pipe 是像文件对象 . Return pair (transport, protocol) ，其中 transport 支持 ReadTransport 接口。

采用 SelectorEventLoop event loop, the pipe is set to non-blocking mode.

此方法是协程 .

协程 BaseEventLoop. connect_write_pipe ( protocol_factory , pipe ) ¶

protocol_factory should instantiate object with BaseProtocol 接口。 pipe is 像文件对象 . Return pair (transport, protocol) ，其中 transport supports WriteTransport 接口。

采用 SelectorEventLoop event loop, the pipe is set to non-blocking mode.

此方法是协程 .

另请参阅

The BaseEventLoop.subprocess_exec() and BaseEventLoop.subprocess_shell() 方法。

18.5.1.11. UNIX signals ¶

Availability: UNIX only.

BaseEventLoop. add_signal_handler ( signum , callback , *args ) ¶

Add a handler for a signal.

引发 ValueError if the signal number is invalid or uncatchable. Raise RuntimeError if there is a problem setting up the handler.

Use functools.partial to pass keywords to the callback .

BaseEventLoop. remove_signal_handler ( sig ) ¶

Remove a handler for a signal.

返回 True if a signal handler was removed, False 若不。

另请参阅

The signal 模块。

18.5.1.12. Executor ¶

Call a function in an Executor (pool of threads or pool of processes). By default, an event loop uses a thread pool executor ( ThreadPoolExecutor ).

协程 BaseEventLoop. run_in_executor ( executor , func , *args ) ¶

Arrange for a func to be called in the specified executor.

The executor argument should be an Executor instance. The default executor is used if executor is None .

Use functools.partial to pass keywords to the *func* .

此方法是协程 .

BaseEventLoop. set_default_executor ( executor ) ¶: Set the default executor used by run_in_executor() .

18.5.1.13. Error Handling API ¶

Allows to customize how exceptions are handled in the event loop.

BaseEventLoop. set_exception_handler ( handler ) ¶

Set handler as the new event loop exception handler.

若 handler is None , the default exception handler will be set.

若 handler is a callable object, it should have a matching signature to (loop, context) ，其中 loop will be a reference to the active event loop, context 将是 dict object (see call_exception_handler() documentation for details about context).

BaseEventLoop. default_exception_handler ( context ) ¶

默认异常处理程序。

This is called when an exception occurs and no exception handler is set, and can be called by a custom exception handler that wants to defer to the default behavior.

context parameter has the same meaning as in call_exception_handler() .

BaseEventLoop. call_exception_handler ( context ) ¶

Call the current event loop exception handler.

context 是 dict object containing the following keys (new keys may be introduced later):

‘message’: Error message;
‘exception’ (optional): Exception object;
‘future’ (optional): asyncio.Future 实例；
‘handle’ (optional): asyncio.Handle 实例；
‘protocol’ (optional): Protocol 实例；
‘transport’ (optional): Transport 实例；
‘socket’ (optional): socket.socket 实例。

注意

Note: this method should not be overloaded in subclassed event loops. For any custom exception handling, use set_exception_handler() 方法。

18.5.1.14. Debug mode ¶

BaseEventLoop. get_debug ( ) ¶

获取调试模式 ( bool ) of the event loop.

默认值为 True if the environment variable PYTHONASYNCIODEBUG is set to a non-empty string, False 否则。

3.4.2 版新增。

BaseEventLoop. set_debug ( enabled: bool ) ¶

Set the debug mode of the event loop.

3.4.2 版新增。

另请参阅

The asyncio 的调试模式 .

18.5.1.15. Server ¶

class asyncio. Server ¶

Server listening on sockets.

Object created by the BaseEventLoop.create_server() 方法和 start_server() function. Don’t instantiate the class directly.

close ( ) ¶

协程 wait_closed ( ) ¶

等待直到 close() method completes.

此方法是协程 .

sockets ¶: List of socket.socket objects the server is listening to, or None if the server is closed.

18.5.1.16. Handle ¶

class asyncio. Handle ¶: A callback wrapper object returned by BaseEventLoop.call_soon() , BaseEventLoop.call_soon_threadsafe() , BaseEventLoop.call_later() ，和 BaseEventLoop.call_at() .

cancel ( ) ¶

18.5.1.17. Event loop examples ¶

18.5.1.17.1. Hello World with call_soon() ¶

Example using the BaseEventLoop.call_soon() method to schedule a callback. The callback displays "Hello World" and then stops the event loop:

import asyncio
def hello_world(loop):
    print('Hello World')
    loop.stop()
loop = asyncio.get_event_loop()
# Schedule a call to hello_world()
loop.call_soon(hello_world, loop)
# Blocking call interrupted by loop.stop()
loop.run_forever()
loop.close()

另请参阅

The Hello World coroutine example uses a 协程 .

18.5.1.17.2. Display the current date with call_later() ¶

Example of callback displaying the current date every second. The callback uses the BaseEventLoop.call_later() method to reschedule itself during 5 seconds, and then stops the event loop:

import asyncio
import datetime
def display_date(end_time, loop):
    print(datetime.datetime.now())
    if (loop.time() + 1.0) < end_time:
        loop.call_later(1, display_date, end_time, loop)
    else:
        loop.stop()
loop = asyncio.get_event_loop()
# Schedule the first call to display_date()
end_time = loop.time() + 5.0
loop.call_soon(display_date, end_time, loop)
# Blocking call interrupted by loop.stop()
loop.run_forever()
loop.close()

另请参阅

The coroutine displaying the current date example uses a 协程 .

18.5.1.17.3. Watch a file descriptor for read events ¶

Wait until a file descriptor received some data using the BaseEventLoop.add_reader() method and then close the event loop:

import asyncio
try:
    from socket import socketpair
except ImportError:
    from asyncio.windows_utils import socketpair
# Create a pair of connected file descriptors
rsock, wsock = socketpair()
loop = asyncio.get_event_loop()
def reader():
    data = rsock.recv(100)
    print("Received:", data.decode())
    # We are done: unregister the file descriptor
    loop.remove_reader(rsock)
    # Stop the event loop
    loop.stop()
# Register the file descriptor for read event
loop.add_reader(rsock, reader)
# Simulate the reception of data from the network
loop.call_soon(wsock.send, 'abc'.encode())
# Run the event loop
loop.run_forever()
# We are done, close sockets and the event loop
rsock.close()
wsock.close()
loop.close()

另请参阅

The 注册打开套接字等待使用协议的数据 example uses a low-level protocol created by the BaseEventLoop.create_connection() 方法。

The register an open socket to wait for data using streams example uses high-level streams created by the open_connection() function in a coroutine.

18.5.1.17.4. Set signal handlers for SIGINT and SIGTERM ¶

import asyncio
import functools
import os
import signal
def ask_exit(signame):
    print("got signal %s: exit" % signame)
    loop.stop()
loop = asyncio.get_event_loop()
for signame in ('SIGINT', 'SIGTERM'):
    loop.add_signal_handler(getattr(signal, signame),
                            functools.partial(ask_exit, signame))
print("Event loop running forever, press Ctrl+C to interrupt.")
print("pid %s: send SIGINT or SIGTERM to exit." % os.getpid())
try:
    loop.run_forever()
finally:
    loop.close()

此范例仅工作于 UNIX。

18.5.1. 基事件循环 ¶

18.5.1.1. 运行事件循环 ¶

18.5.1.2. 调用 ¶

18.5.1.3. 延迟调用 ¶

18.5.1.4. Tasks ¶

18.5.1.5. Creating connections ¶

18.5.1.6. Creating listening connections ¶

18.5.1.7. Watch file descriptors ¶

18.5.1.8. Low-level socket operations ¶

18.5.1.9. Resolve host name ¶

18.5.1.10. Connect pipes ¶

18.5.1.11. UNIX signals ¶

18.5.1.12. Executor ¶

18.5.1.13. Error Handling API ¶

18.5.1.14. Debug mode ¶

18.5.1.15. Server ¶

18.5.1.16. Handle ¶

18.5.1.17. Event loop examples ¶

18.5.1.17.1. Hello World with call_soon() ¶

18.5.1.17.2. Display the current date with call_later() ¶

18.5.1.17.3. Watch a file descriptor for read events ¶

18.5.1.17.4. Set signal handlers for SIGINT and SIGTERM ¶

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