18.5.1. 基事件循环 ¶

18.5.1.1. 运行事件循环 ¶

AbstractEventLoop. run_forever ( ) ¶

Run until stop() is called. If stop() is called before run_forever() is called, this polls the I/O selector once with a timeout of zero, runs all callbacks scheduled in response to I/O events (and those that were already scheduled), and then exits. If stop() is called while run_forever() is running, this will run the current batch of callbacks and then exit. Note that callbacks scheduled by callbacks will not run in that case; they will run the next time run_forever() 被调用。

3.5.1 版改变。

AbstractEventLoop. run_until_complete ( future ) ¶

运行直到 Future 完成。

If the argument is a coroutine object , it is wrapped by ensure_future() .

Return the Future’s result, or raise its exception.

AbstractEventLoop. is_running ( ) ¶

返回事件循环的运行状态。

AbstractEventLoop. stop ( ) ¶

停止运行事件循环。

This causes run_forever() to exit at the next suitable opportunity (see there for more details).

3.5.1 版改变。

AbstractEventLoop. is_closed ( ) ¶

返回 True 若事件循环被关闭。

3.4.2 版新增。

AbstractEventLoop. close ( ) ¶

Close the event loop. The loop must not be running. Pending callbacks will be lost.

This clears the queues and shuts down the executor, but does not wait for the executor to finish.

This is idempotent and irreversible. No other methods should be called after this one.

协程 AbstractEventLoop. shutdown_asyncgens ( ) ¶

Schedule all currently open 异步生成器 objects to close with an aclose() call. After calling this method, the event loop will issue a warning whenever a new asynchronous generator is iterated. Should be used to finalize all scheduled asynchronous generators reliably. Example:

try:
    loop.run_forever()
finally:
    loop.run_until_complete(loop.shutdown_asyncgens())
    loop.close()
										

3.6 版新增。

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)) will call print("Hello", flush=True) .

AbstractEventLoop. call_soon ( callback , *args ) ¶

Arrange for a callback to be called as soon as possible. The callback is called after call_soon() returns, when control returns to the event loop.

This operates as a FIFO queue, callbacks are called in the order in which they are registered. Each callback will be called exactly once.

Any positional arguments after the callback will be passed to the callback when it is called.

An instance of asyncio.Handle is returned, which can be used to cancel the callback.

Use functools.partial to pass keywords to the callback .

AbstractEventLoop. call_soon_threadsafe ( callback , *args ) ¶

像 call_soon() ，但线程安全。

见 并发和多线程 section of the documentation.

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() .

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

Arrange for the callback to be called after the given delay seconds (either an int or float).

An instance of asyncio.Handle is returned, which can be used to cancel the callback.

callback will be called exactly once per call to call_later() . If two callbacks are scheduled for exactly the same time, it is undefined which will be called first.

The optional positional args will be passed to the callback when it is called. If you want the callback to be called with some named arguments, use a closure or functools.partial() .

Use functools.partial to pass keywords to the callback .

AbstractEventLoop. call_at ( when , callback , *args ) ¶

Arrange for the callback to be called at the given absolute timestamp when (an int or float), using the same time reference as AbstractEventLoop.time() .

This method’s behavior is the same as call_later() .

An instance of asyncio.Handle is returned, which can be used to cancel the callback.

Use functools.partial to pass keywords to the callback .

AbstractEventLoop. time ( ) ¶

Return the current time, as a float value, according to the event loop’s internal clock.

18.5.1.4. Futures ¶

AbstractEventLoop. create_future ( ) ¶

创建 asyncio.Future object attached to the loop.

This is a preferred way to create futures in asyncio, as event loop implementations can provide alternative implementations of the Future class (with better performance or instrumentation).

3.5.2 版新增。

18.5.1.5. 任务 ¶

AbstractEventLoop. create_task ( coro ) ¶

Schedule the execution of a coroutine object : wrap it in a future. Return a Task 对象。

Third-party event loops can use their own subclass of Task for interoperability. In this case, the result type is a subclass of Task .

This method was added in Python 3.4.2. Use the async() function to support also older Python versions.

3.4.2 版新增。

AbstractEventLoop. set_task_factory ( factory ) ¶

Set a task factory that will be used by AbstractEventLoop.create_task() .

若 factory is None the default task factory will be set.

若 factory 是 callable , it should have a signature matching (loop, coro) ，其中 loop will be a reference to the active event loop, coro will be a coroutine object. The callable must return an asyncio.Future compatible object.

3.4.4 版新增。

AbstractEventLoop. get_task_factory ( ) ¶

Return a task factory, or None if the default one is in use.

3.4.4 版新增。

18.5.1.6. 创建连接 ¶

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

Create a streaming transport connection to a given Internet host and port : socket family AF_INET or AF_INET6 depending on host (或 family if specified), socket type SOCK_STREAM . protocol_factory must be a callable returning a protocol 实例。

此方法是 协程 which will try to establish the connection in the background. When successful, the coroutine returns a (transport, protocol) 对。

The chronological synopsis of the underlying operation is as follows:

1. The connection is established, and a transport is created to represent it.
2. protocol_factory is called without arguments and must return a protocol 实例。
3. The protocol instance is tied to the transport, and its connection_made() method is called.
4. The coroutine returns successfully with the (transport, protocol) 对。

The created transport is an implementation-dependent bidirectional stream.

注意

protocol_factory can be any kind of callable, not necessarily a class. For example, if you want to use a pre-created protocol instance, you can pass lambda: my_protocol .

Options that change how the connection is created:

• ssl : if given and not false, a SSL/TLS transport is created (by default a plain TCP transport is created). If ssl 是 ssl.SSLContext object, this context is used to create the transport; if ssl is True , a context with some unspecified default settings is used.

  另请参阅

  SSL/TLS 安全注意事项

• server_hostname , is only for use together with ssl , and sets or overrides the hostname that the target server’s certificate will be matched against. By default the value of the host argument is used. If host is empty, there is no default and you must pass a value for server_hostname 。若 server_hostname is an empty string, hostname matching is disabled (which is a serious security risk, allowing for man-in-the-middle-attacks).

• family , proto , flags are the optional address family, protocol and flags to be passed through to getaddrinfo() for host resolution. If given, these should all be integers from the corresponding socket module constants.

• sock , if given, should be an existing, already connected socket.socket object to be used by the transport. If sock is given, none of host , port , family , proto , flags and local_addr should be specified.

• local_addr , if given, is a (local_host, local_port) tuple used to bind the socket to locally. The local_host and local_port are looked up using getaddrinfo(), similarly to host and port .

3.5 版改变： 在 Windows 采用 ProactorEventLoop ，现在支持 SSL/TLS。

另请参阅

open_connection() function can be used to get a pair of ( StreamReader , StreamWriter ) instead of a protocol.

协程 AbstractEventLoop. 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 ) ¶

Create datagram connection: socket family AF_INET or AF_INET6 depending on host (或 family if specified), socket type SOCK_DGRAM . protocol_factory must be a callable returning a protocol 实例。

此方法是 协程 which will try to establish the connection in the background. When successful, the coroutine returns a (transport, protocol) 对。

Options changing how the connection is created:

• local_addr , if given, is a (local_host, local_port) tuple used to bind the socket to locally. The local_host and local_port are looked up using getaddrinfo() .
• remote_addr , if given, is a (remote_host, remote_port) tuple used to connect the socket to a remote address. The remote_host and remote_port are looked up using getaddrinfo() .
• family , proto , flags are the optional address family, protocol and flags to be passed through to getaddrinfo() for host resolution. If given, these should all be integers from the corresponding socket module constants.
• reuse_address tells the kernel to reuse a local socket in TIME_WAIT state, without waiting for its natural timeout to expire. If not specified will automatically be set to True on UNIX.
• reuse_port tells the kernel to allow this endpoint to be bound to the same port as other existing endpoints are bound to, so long as they all set this flag when being created. This option is not supported on Windows and some UNIX’s. If the SO_REUSEPORT constant is not defined then this capability is unsupported.
• allow_broadcast tells the kernel to allow this endpoint to send messages to the broadcast address.
• sock can optionally be specified in order to use a preexisting, already connected, socket.socket object to be used by the transport. If specified, local_addr and remote_addr should be omitted (must be None ).

在 Windows 采用 ProactorEventLoop , this method is not supported.

见 UDP echo client protocol and UDP echo server protocol 范例。

3.4.4 版改变： family , proto , flags , reuse_address , reuse_port, *allow_broadcast ，和 sock parameters were added.

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

Create UNIX connection: socket family AF_UNIX , socket type SOCK_STREAM 。 AF_UNIX socket family is used to communicate between processes on the same machine efficiently.

此方法是 协程 which will try to establish the connection in the background. When successful, the coroutine returns a (transport, protocol) 对。

path is the name of a UNIX domain socket, and is required unless a sock parameter is specified. Abstract UNIX sockets, str ，和 bytes paths are supported.

见 AbstractEventLoop.create_connection() method for parameters.

可用性：UNIX。

18.5.1.7. 创建监听连接 ¶

协程 AbstractEventLoop. 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 ) ¶

Create a TCP server (socket type SOCK_STREAM ) bound to host and port .

返回 Server object, its sockets attribute contains created sockets. Use the Server.close() method to stop the server: close listening sockets.

参数：

• host parameter can be a string, in that case the TCP server is bound to host and port 。 host parameter can also be a sequence of strings and in that case the TCP server is bound to all hosts of the sequence. If host is an empty string or None , all interfaces are assumed and a list of multiple sockets will be returned (most likely one for IPv4 and another one for IPv6).
• family can be set to either socket.AF_INET or AF_INET6 to force the socket to use IPv4 or IPv6. If not set it will be determined from host (defaults to socket.AF_UNSPEC ).
• flags is a bitmask for getaddrinfo() .
• sock can optionally be specified in order to use a preexisting socket object. If specified, host and port should be omitted (must be None ).
• backlog is the maximum number of queued connections passed to listen() (defaults to 100).
• ssl can be set to an SSLContext to enable SSL over the accepted connections.
• reuse_address tells the kernel to reuse a local socket in TIME_WAIT state, without waiting for its natural timeout to expire. If not specified will automatically be set to True on UNIX.
• reuse_port tells the kernel to allow this endpoint to be bound to the same port as other existing endpoints are bound to, so long as they all set this flag when being created. This option is not supported on Windows.

此方法是 协程 .

3.5 版改变： 在 Windows 采用 ProactorEventLoop ，现在支持 SSL/TLS。

另请参阅

函数 start_server() creates a ( StreamReader , StreamWriter ) pair and calls back a function with this pair.

3.5.1 版改变： host parameter can now be a sequence of strings.

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

类似 AbstractEventLoop.create_server() , but specific to the socket family AF_UNIX .

此方法是 协程 .

可用性：UNIX。

协程 BaseEventLoop. connect_accepted_socket ( protocol_factory , sock , * , ssl=None ) ¶

Handle an accepted connection.

This is used by servers that accept connections outside of asyncio but that use asyncio to handle them.

参数：

• sock is a preexisting socket object returned from an accept 调用。
• ssl can be set to an SSLContext to enable SSL over the accepted connections.

此方法是 协程 . When completed, the coroutine returns a (transport, protocol) 对。

3.5.3 版新增。

18.5.1.8. 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.

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

Start watching the file descriptor for read availability and then call the callback with specified arguments.

Use functools.partial to pass keywords to the callback .

AbstractEventLoop. remove_reader ( fd ) ¶

Stop watching the file descriptor for read availability.

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

Start watching the file descriptor for write availability and then call the callback with specified arguments.

Use functools.partial to pass keywords to the callback .

AbstractEventLoop. remove_writer ( fd ) ¶

Stop watching the file descriptor for write availability.

watch a file descriptor for read events example uses the low-level AbstractEventLoop.add_reader() method to register the file descriptor of a socket.

18.5.1.9. 低级套接字操作 ¶

协程 AbstractEventLoop. sock_recv ( sock , nbytes ) ¶

Receive data from the socket. Modeled after blocking socket.socket.recv() 方法。

The return value is a bytes object representing the data received. The maximum amount of data to be received at once is specified by nbytes .

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

此方法是 协程 .

协程 AbstractEventLoop. sock_sendall ( sock , data ) ¶

Send data to the socket. Modeled after blocking socket.socket.sendall() 方法。

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.

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

此方法是 协程 .

协程 AbstractEventLoop. sock_connect ( sock , address ) ¶

Connect to a remote socket at address . Modeled after blocking socket.socket.connect() 方法。

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

此方法是 协程 .

3.5.2 版改变： address no longer needs to be resolved. sock_connect will try to check if the address is already resolved by calling socket.inet_pton() . If not, AbstractEventLoop.getaddrinfo() will be used to resolve the address .

另请参阅

AbstractEventLoop.create_connection() and asyncio.open_connection() .

协程 AbstractEventLoop. sock_accept ( sock ) ¶

Accept a connection. Modeled after blocking socket.socket.accept() .

The socket must be bound to an address and listening for connections. The return value is a pair (conn, address) where conn 是 new socket object usable to send and receive data on the connection, and address is the address bound to the socket on the other end of the connection.

The socket sock must be non-blocking.

此方法是 协程 .

另请参阅

AbstractEventLoop.create_server() and start_server() .

18.5.1.10. Resolve host name ¶

协程 AbstractEventLoop. 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 AbstractEventLoop. getnameinfo ( sockaddr , flags=0 ) ¶

此方法是 协程 ，类似 socket.getnameinfo() 函数但非阻塞。

18.5.1.11. 连接管道 ¶

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

协程 AbstractEventLoop. connect_read_pipe ( protocol_factory , pipe ) ¶

Register read pipe in eventloop.

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。

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

此方法是 协程 .

协程 AbstractEventLoop. connect_write_pipe ( protocol_factory , pipe ) ¶

Register write pipe in eventloop.

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。

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

此方法是 协程 .

18.5.1.12. UNIX 信号 ¶

Availability: UNIX only.

AbstractEventLoop. 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 .

AbstractEventLoop. remove_signal_handler ( sig ) ¶

Remove a handler for a signal.

返回 True if a signal handler was removed, False if not.

18.5.1.13. 执行器 ¶

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 AbstractEventLoop. run_in_executor ( executor , func , *args ) ¶

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

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 .

Changed in version 3.5.3: BaseEventLoop.run_in_executor() no longer configures the max_workers of the thread pool executor it creates, instead leaving it up to the thread pool executor ( ThreadPoolExecutor ) to set the default.

AbstractEventLoop. set_default_executor ( executor ) ¶

Set the default executor used by run_in_executor() .

18.5.1.14. 错误处理 API ¶

Allows customizing how exceptions are handled in the event loop.

AbstractEventLoop. 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 will be a dict object (see call_exception_handler() documentation for details about context).

AbstractEventLoop. get_exception_handler ( ) ¶

Return the exception handler, or None if the default one is in use.

3.5.2 版新增。

AbstractEventLoop. 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() .

AbstractEventLoop. 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。

18.5.1.15. 调试模式 ¶

AbstractEventLoop. get_debug ( ) ¶

Get the debug mode ( 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。

AbstractEventLoop. set_debug ( enabled: bool ) ¶

Set the debug mode of the event loop.

3.4.2 版新增。

18.5.1.16. 服务器 ¶

class asyncio. Server ¶

Server listening on sockets.

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

close ( ) ¶

Stop serving: close listening sockets and set the sockets attribute to None .

The sockets that represent existing incoming client connections are left open.

The server is closed asynchronously, use the wait_closed() coroutine to wait until the server is closed.

协程 wait_closed ( ) ¶

Wait until the 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.

18.5.1.17. Handle ¶

class asyncio. Handle ¶

A callback wrapper object returned by AbstractEventLoop.call_soon() , AbstractEventLoop.call_soon_threadsafe() , AbstractEventLoop.call_later() ，和 AbstractEventLoop.call_at() .

cancel ( ) ¶

Cancel the call. If the callback is already canceled or executed, this method has no effect.

18.5.1.18. 事件循环范例 ¶

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()
									

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()
									

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()
									

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()