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python - Requests/aiohttp：关闭响应对象

问题描述

我对在和.close()中都需要响应对象感到有些困惑。（请注意，这是一个单独的实例方法，而不是——我说的是响应对象本身。）requestsaiohttpsession.close()

一些简单的测试（如下）似乎暗示响应在会话上下文管理器中定义时会自动关闭。 （它本身调用or 。但这是 Session 的关闭，而不是 Response 对象。self.close()）__exit____aexit__

例子 -requests

>>> import requests
>>> 
>>> with requests.Session() as s:
...     resp = s.request('GET', 'https://www.pastebin.com')
...     resp.raise_for_status()
...     print(resp.raw.closed)  # `raw` is urllib3.response.HTTPResponse object
...     print(resp.raw._pool)
...     print(resp.raw._connection)
...     c = resp.text
... 
True
HTTPSConnectionPool(host='pastebin.com', port=443)
None
>>>
>>> while 1:
...     print(resp.raw.closed)
...     print(resp.raw._pool)
...     print(resp.raw._connection)
...     break
... 
True
HTTPSConnectionPool(host='pastebin.com', port=443)
None

例子 -aiohttp

>>> import asyncio
>>> import aiohttp
>>>
>>> async def get():
...     async with aiohttp.ClientSession() as s:
...         # The response is already closed after this `with` block.
...         # Why would it need to be used as a context manager?
...         resp = await s.request('GET', 'https://www.pastebin.com')
...         print(resp._closed)
...         print(resp._connection)
...         print(resp._released)
...         c = await resp.text()
...     print()
...     print(resp._closed)
...     print(resp._connection)
...     print(resp._released)
...     return c
... 
>>> c = asyncio.run(get())  # Python 3.7 +
False
Connection<ConnectionKey(host='pastebin.com', port=443, is_ssl=True, ssl=None, proxy=None, proxy_auth=None, proxy_headers_hash=None)>
False

True
None
False

这是 的来源requests.models.Response。“通常不需要显式调用”是什么意思？有哪些例外？

def close(self):
    """Releases the connection back to the pool. Once this method has been
    called the underlying ``raw`` object must not be accessed again.
    *Note: Should not normally need to be called explicitly.*
    """
    if not self._content_consumed:
        self.raw.close()

    release_conn = getattr(self.raw, 'release_conn', None)
    if release_conn is not None:
        release_conn()

标签： pythonpython-requestsaiohttppython-3.7

解决方案

Requests: 你不需要显式调用close(). 完成后请求将自动关闭，因为它基于 urlopen（这就是为什么resp.raw.closed是 True），这是我观看后的简化session.py代码adapters.py：

from urllib3 import PoolManager
import time
manager = PoolManager(10)
conn = manager.connection_from_host('host1.example.com')
conn2 = manager.connection_from_host('host2.example.com')
res = conn.urlopen(url="http://host1.example.com/",method="get")
print(len(manager.pools))
manager.clear()
print(len(manager.pools))
print(res.closed)

#2
#0
#True

然后做了__exit__什么？它用于清除PoolManager(self.poolmanager=PoolManager(...))和proxy。

# session.py
def __exit__(self, *args): #line 423
    self.close()
def close(self): #line 733
    for v in self.adapters.values():
        v.close()

# adapters.py
# v.close()
def close(self): #line 307
        self.poolmanager.clear()
        for proxy in self.proxy_manager.values():
            proxy.clear()

所以你什么时候需要使用close()，正如注释所说的释放连接回池，因为DEFAULT_POOLSIZE = 10（http/https是独立的）。这意味着如果您想通过一个会话访问超过 10 个网站，您可以选择关闭一些您不需要的网站，否则当您有一个会话时，管理员将关闭从第一个到最新的连接。但实际上你不需要关心这个，你可以指定池大小，它不会浪费太多时间来重建连接。

aiohttpaiohttp.ClientSession() 对所有请求使用一个 TCPConnector。当它触发时__aexit__， self._connector将被关闭。

编辑：s.request()设置了来自主机的连接，但没有得到响应。await resp.text()只有在得到响应后才能执行，如果您没有执行此步骤（等待响应），您将退出而没有响应。

if connector is None: #line 132
    connector = TCPConnector(loop=loop)
...
self._connector = connector #line 151
# connection timeout
try:
    with CeilTimeout(real_timeout.connect,loop=self._loop):
    assert self._connector is not None
    conn = await self._connector.connect(
        req,
        traces=traces,
        timeout=real_timeout
        )
...
async def close(self) -> None:
        if not self.closed:
            if self._connector is not None and self._connector_owner:
                self._connector.close()
            self._connector = None
...
async def __aexit__(self,
                       ...) -> None:
        await self.close()

这是显示我所说的代码

import asyncio
import aiohttp
import time

async def get():
    async with aiohttp.ClientSession() as s:
        # The response is already closed after this `with` block.
        # Why would it need to be used as a context manager?
        resp = await s.request('GET', 'https://www.stackoverflow.com')
        resp2 = await s.request('GET', 'https://www.github.com')
        print("resp:",resp._closed)
        print("resp:",resp._connection)
        print("resp2:",resp2._closed)
        print("resp2:",resp2._connection)
        s.close()
        print(s.closed)
        c = await resp.text()
        d = await resp2.text()

    print()
    print(s._connector)
    print("resp:",resp._closed)
    print("resp:",resp._connection)
    print("resp2:",resp2._closed)
    print("resp2:",resp2._connection)

loop = asyncio.get_event_loop()
loop.run_until_complete(get())  # Python 3.5 +

#dead loop

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