| .. currentmodule:: asyncio |
| |
| .. _asyncio-streams: |
| |
| ++++++++++++++++++++++++ |
| Streams (high-level API) |
| ++++++++++++++++++++++++ |
| |
| Stream functions |
| ================ |
| |
| .. function:: open_connection(host=None, port=None, \*, loop=None, limit=None, **kwds) |
| |
| A wrapper for :meth:`~BaseEventLoop.create_connection()` returning a (reader, |
| writer) pair. |
| |
| The reader returned is a :class:`StreamReader` instance; the writer is |
| a :class:`StreamWriter` instance. |
| |
| The arguments are all the usual arguments to |
| :meth:`BaseEventLoop.create_connection` except *protocol_factory*; most |
| common are positional host and port, with various optional keyword arguments |
| following. |
| |
| Additional optional keyword arguments are *loop* (to set the event loop |
| instance to use) and *limit* (to set the buffer limit passed to the |
| :class:`StreamReader`). |
| |
| (If you want to customize the :class:`StreamReader` and/or |
| :class:`StreamReaderProtocol` classes, just copy the code -- there's really |
| nothing special here except some convenience.) |
| |
| This function is a :ref:`coroutine <coroutine>`. |
| |
| .. function:: start_server(client_connected_cb, host=None, port=None, \*, loop=None, limit=None, **kwds) |
| |
| Start a socket server, with a callback for each client connected. The return |
| value is the same as :meth:`~BaseEventLoop.create_server()`. |
| |
| The *client_connected_cb* parameter is called with two parameters: |
| *client_reader*, *client_writer*. *client_reader* is a |
| :class:`StreamReader` object, while *client_writer* is a |
| :class:`StreamWriter` object. The *client_connected_cb* parameter can |
| either be a plain callback function or a :ref:`coroutine function |
| <coroutine>`; if it is a coroutine function, it will be automatically |
| converted into a :class:`Task`. |
| |
| The rest of the arguments are all the usual arguments to |
| :meth:`~BaseEventLoop.create_server()` except *protocol_factory*; most |
| common are positional *host* and *port*, with various optional keyword |
| arguments following. |
| |
| Additional optional keyword arguments are *loop* (to set the event loop |
| instance to use) and *limit* (to set the buffer limit passed to the |
| :class:`StreamReader`). |
| |
| This function is a :ref:`coroutine <coroutine>`. |
| |
| .. function:: open_unix_connection(path=None, \*, loop=None, limit=None, **kwds) |
| |
| A wrapper for :meth:`~BaseEventLoop.create_unix_connection()` returning |
| a (reader, writer) pair. |
| |
| See :func:`open_connection` for information about return value and other |
| details. |
| |
| This function is a :ref:`coroutine <coroutine>`. |
| |
| Availability: UNIX. |
| |
| .. function:: start_unix_server(client_connected_cb, path=None, \*, loop=None, limit=None, **kwds) |
| |
| Start a UNIX Domain Socket server, with a callback for each client connected. |
| |
| See :func:`start_server` for information about return value and other |
| details. |
| |
| This function is a :ref:`coroutine <coroutine>`. |
| |
| Availability: UNIX. |
| |
| |
| StreamReader |
| ============ |
| |
| .. class:: StreamReader(limit=None, loop=None) |
| |
| .. method:: exception() |
| |
| Get the exception. |
| |
| .. method:: feed_eof() |
| |
| Acknowledge the EOF. |
| |
| .. method:: feed_data(data) |
| |
| Feed *data* bytes in the internal buffer. Any operations waiting |
| for the data will be resumed. |
| |
| .. method:: set_exception(exc) |
| |
| Set the exception. |
| |
| .. method:: set_transport(transport) |
| |
| Set the transport. |
| |
| .. method:: read(n=-1) |
| |
| Read up to *n* bytes. If *n* is not provided, or set to ``-1``, |
| read until EOF and return all read bytes. |
| |
| If the EOF was received and the internal buffer is empty, |
| return an empty ``bytes`` object. |
| |
| This method is a :ref:`coroutine <coroutine>`. |
| |
| .. method:: readline() |
| |
| Read one line, where "line" is a sequence of bytes ending with ``\n``. |
| |
| If EOF is received, and ``\n`` was not found, the method will |
| return the partial read bytes. |
| |
| If the EOF was received and the internal buffer is empty, |
| return an empty ``bytes`` object. |
| |
| This method is a :ref:`coroutine <coroutine>`. |
| |
| .. method:: readexactly(n) |
| |
| Read exactly *n* bytes. Raise an :exc:`IncompleteReadError` if the end of |
| the stream is reached before *n* can be read, the |
| :attr:`IncompleteReadError.partial` attribute of the exception contains |
| the partial read bytes. |
| |
| This method is a :ref:`coroutine <coroutine>`. |
| |
| .. method:: at_eof() |
| |
| Return ``True`` if the buffer is empty and :meth:`feed_eof` was called. |
| |
| |
| StreamWriter |
| ============ |
| |
| .. class:: StreamWriter(transport, protocol, reader, loop) |
| |
| Wraps a Transport. |
| |
| This exposes :meth:`write`, :meth:`writelines`, :meth:`can_write_eof()`, |
| :meth:`write_eof`, :meth:`get_extra_info` and :meth:`close`. It adds |
| :meth:`drain` which returns an optional :class:`Future` on which you can |
| wait for flow control. It also adds a transport attribute which references |
| the :class:`Transport` directly. |
| |
| .. attribute:: transport |
| |
| Transport. |
| |
| .. method:: can_write_eof() |
| |
| Return :const:`True` if the transport supports :meth:`write_eof`, |
| :const:`False` if not. See :meth:`WriteTransport.can_write_eof`. |
| |
| .. method:: close() |
| |
| Close the transport: see :meth:`BaseTransport.close`. |
| |
| .. method:: drain() |
| |
| Wait until the write buffer of the underlying transport is flushed. |
| |
| The intended use is to write:: |
| |
| w.write(data) |
| yield from w.drain() |
| |
| When the transport buffer is full (the protocol is paused), block until |
| the buffer is (partially) drained and the protocol is resumed. When there |
| is nothing to wait for, the yield-from continues immediately. |
| |
| This method is a :ref:`coroutine <coroutine>`. |
| |
| .. method:: get_extra_info(name, default=None) |
| |
| Return optional transport information: see |
| :meth:`BaseTransport.get_extra_info`. |
| |
| .. method:: write(data) |
| |
| Write some *data* bytes to the transport: see |
| :meth:`WriteTransport.write`. |
| |
| .. method:: writelines(data) |
| |
| Write a list (or any iterable) of data bytes to the transport: |
| see :meth:`WriteTransport.writelines`. |
| |
| .. method:: write_eof() |
| |
| Close the write end of the transport after flushing buffered data: |
| see :meth:`WriteTransport.write_eof`. |
| |
| |
| StreamReaderProtocol |
| ==================== |
| |
| .. class:: StreamReaderProtocol(stream_reader, client_connected_cb=None, loop=None) |
| |
| Trivial helper class to adapt between :class:`Protocol` and |
| :class:`StreamReader`. Sublclass of :class:`Protocol`. |
| |
| *stream_reader* is a :class:`StreamReader` instance, *client_connected_cb* |
| is an optional function called with (stream_reader, stream_writer) when a |
| connection is made, *loop* is the event loop instance to use. |
| |
| (This is a helper class instead of making :class:`StreamReader` itself a |
| :class:`Protocol` subclass, because the :class:`StreamReader` has other |
| potential uses, and to prevent the user of the :class:`StreamReader` to |
| accidentally call inappropriate methods of the protocol.) |
| |
| |
| IncompleteReadError |
| =================== |
| |
| .. exception:: IncompleteReadError |
| |
| Incomplete read error, subclass of :exc:`EOFError`. |
| |
| .. attribute:: expected |
| |
| Total number of expected bytes (:class:`int`). |
| |
| .. attribute:: partial |
| |
| Read bytes string before the end of stream was reached (:class:`bytes`). |
| |
| |
| Stream examples |
| =============== |
| |
| Get HTTP headers |
| ---------------- |
| |
| Simple example querying HTTP headers of the URL passed on the command line:: |
| |
| import asyncio |
| import urllib.parse |
| import sys |
| |
| @asyncio.coroutine |
| def print_http_headers(url): |
| url = urllib.parse.urlsplit(url) |
| if url.scheme == 'https': |
| connect = asyncio.open_connection(url.hostname, 443, ssl=True) |
| else: |
| connect = asyncio.open_connection(url.hostname, 80) |
| reader, writer = yield from connect |
| query = ('HEAD {path} HTTP/1.0\r\n' |
| 'Host: {hostname}\r\n' |
| '\r\n').format(path=url.path or '/', hostname=url.hostname) |
| writer.write(query.encode('latin-1')) |
| while True: |
| line = yield from reader.readline() |
| if not line: |
| break |
| line = line.decode('latin1').rstrip() |
| if line: |
| print('HTTP header> %s' % line) |
| |
| # Ignore the body, close the socket |
| writer.close() |
| |
| url = sys.argv[1] |
| loop = asyncio.get_event_loop() |
| task = asyncio.async(print_http_headers(url)) |
| loop.run_until_complete(task) |
| loop.close() |
| |
| Usage:: |
| |
| python example.py http://example.com/path/page.html |
| |