Requests/aiohttp：关闭响应对象

我对是否需要感到有点困惑.close()两者中的响应对象requests and aiohttp。 （请注意，这是一个单独的实例方法，而不是session.close()--我说的是响应对象本身。）

• Does Response (requests) or ClientResponse (aiohttp）曾经需要显式调用.close()?
• 如果不是，那么使用响应本身作为上下文管理器的目的是什么？ （async with session.request('GET', 'https://www.pastebin.com'）如下。）如果如下所示隐式关闭，为什么要为此定义两个 dunder 方法？

一些简单的测试（如下）似乎意味着当在会话上下文管理器内部定义响应时，响应会自动关闭。（这本身就称为self.close() in __exit__ or __aexit__。但这是会话的关闭，而不是响应对象的关闭。）

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

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

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()

Requests：您不需要显式调用close()。 request 完成后会自动关闭，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代码session.py and 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

然后做了什么__exit__做？它用于清除PoolManager(self.poolmanager=PoolManager(...)) and 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()

那么什么时候你需要使用close()，正如注释所说将连接释放回池中， 因为DEFAULT_POOLSIZE = 10（http/https 是独立的）。这意味着如果您想在一个会话中访问 10 个以上的网站，您可以选择关闭一些您不需要的网站，否则当您有多个网站时，管理器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，并且不会浪费太多时间来重建连接

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

Edit: s.request()已与主机建立连接，但未得到响应。await resp.text()只能在得到响应后执行，如果您没有执行此步骤（等待响应），您将在没有响应的情况下退出。

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()

这是显示我所说内容的代码

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