Requests06.设置超时时间

如果服务器响应时间过长，导致requests长时间持续请求。可以使用timeout来指定超时时间，当响应超过指定的时间后，将抛出Timeout异常。
requests设置超时时间包括两部分：

1. 连接超时时间
   连接时间指的是在requests请求服务器，并与服务器相连接所花费的时间。
2. 读取超时时间
   读取时间指的是在请求与服务器连接后，服务器处理业务逻辑并将数据返回至客户端所花费的时间。

requests的timeout参数有三种传入方式：

1. 单值传入
   单纯地传入一个数字，用于指定总的超时时间（单位：秒），该超时时间包括连接超时时间和读取超时时间。若在指定的超时时间内，requests在连接阶段，将抛出requests.exceptions.ConnectTimeout异常；requests在读取阶段，将抛出requests.exceptions.ReadTimeout异常。

• 连接超时异常：

import requests

if __name__ == '__main__':
    r = requests.post("http://httpbin.org/post", timeout=0.3)

设置超时时间为0.3秒，若在0.3秒内请求未能与服务器连接成功，将输出：

Traceback (most recent call last):
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connection.py", line 160, in _new_conn
    (self._dns_host, self.port), self.timeout, **extra_kw)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\util\connection.py", line 80, in create_connection
    raise err
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\util\connection.py", line 70, in create_connection
    sock.connect(sa)
socket.timeout: timed out

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connectionpool.py", line 603, in urlopen
    chunked=chunked)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connectionpool.py", line 355, in _make_request
    conn.request(method, url, **httplib_request_kw)
  File "D:\DevSoftware\python\lib\http\client.py", line 1244, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "D:\DevSoftware\python\lib\http\client.py", line 1290, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "D:\DevSoftware\python\lib\http\client.py", line 1239, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "D:\DevSoftware\python\lib\http\client.py", line 1026, in _send_output
    self.send(msg)
  File "D:\DevSoftware\python\lib\http\client.py", line 966, in send
    self.connect()
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connection.py", line 183, in connect
    conn = self._new_conn()
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connection.py", line 165, in _new_conn
    (self.host, self.timeout))
urllib3.exceptions.ConnectTimeoutError: (<urllib3.connection.HTTPConnection object at 0x000001A621139E08>, 'Connection to httpbin.org timed out. (connect timeout=0.3)')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\adapters.py", line 449, in send
    timeout=timeout
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connectionpool.py", line 641, in urlopen
    _stacktrace=sys.exc_info()[2])
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\util\retry.py", line 399, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='httpbin.org', port=80): Max retries exceeded with url: /post (Caused by ConnectTimeoutError(<urllib3.connection.HTTPConnection object at 0x000001A621139E08>, 'Connection to httpbin.org timed out. (connect timeout=0.3)'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "D:/git_res/autotest/requests_easy/getweb.py", line 4, in <module>
    r = requests.post("http://httpbin.org/post", timeout=0.3)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\api.py", line 116, in post
    return request('post', url, data=data, json=json, **kwargs)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\api.py", line 60, in request
    return session.request(method=method, url=url, **kwargs)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\sessions.py", line 533, in request
    resp = self.send(prep, **send_kwargs)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\sessions.py", line 646, in send
    r = adapter.send(request, **kwargs)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\adapters.py", line 504, in send
    raise ConnectTimeout(e, request=request)
requests.exceptions.ConnectTimeout: HTTPConnectionPool(host='httpbin.org', port=80): Max retries exceeded with url: /post (Caused by ConnectTimeoutError(<urllib3.connection.HTTPConnection object at 0x000001A621139E08>, 'Connection to httpbin.org timed out. (connect timeout=0.3)'))

Process finished with exit code 1

可以看到最后抛出requests.exceptions.ConnectTimeout异常。

• 读取超时异常

import requests

if __name__ == '__main__':
    r = requests.post("http://httpbin.org/post", timeout=0.35)

设置超时时间为0.35秒，若在此时间内已完成与服务器的连接，但未完成服务器的响应，将输出：

Traceback (most recent call last):
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connectionpool.py", line 387, in _make_request
    six.raise_from(e, None)
  File "<string>", line 2, in raise_from
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connectionpool.py", line 383, in _make_request
    httplib_response = conn.getresponse()
  File "D:\DevSoftware\python\lib\http\client.py", line 1336, in getresponse
    response.begin()
  File "D:\DevSoftware\python\lib\http\client.py", line 306, in begin
    version, status, reason = self._read_status()
  File "D:\DevSoftware\python\lib\http\client.py", line 267, in _read_status
    line = str(self.fp.readline(_MAXLINE + 1), "iso-8859-1")
  File "D:\DevSoftware\python\lib\socket.py", line 589, in readinto
    return self._sock.recv_into(b)
socket.timeout: timed out

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\adapters.py", line 449, in send
    timeout=timeout
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connectionpool.py", line 641, in urlopen
    _stacktrace=sys.exc_info()[2])
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\util\retry.py", line 368, in increment
    raise six.reraise(type(error), error, _stacktrace)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\packages\six.py", line 686, in reraise
    raise value
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connectionpool.py", line 603, in urlopen
    chunked=chunked)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connectionpool.py", line 389, in _make_request
    self._raise_timeout(err=e, url=url, timeout_value=read_timeout)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\urllib3\connectionpool.py", line 307, in _raise_timeout
    raise ReadTimeoutError(self, url, "Read timed out. (read timeout=%s)" % timeout_value)
urllib3.exceptions.ReadTimeoutError: HTTPConnectionPool(host='httpbin.org', port=80): Read timed out. (read timeout=0.35)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "D:/git_res/autotest/requests_easy/getweb.py", line 4, in <module>
    r = requests.post("http://httpbin.org/post", timeout=0.35)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\api.py", line 116, in post
    return request('post', url, data=data, json=json, **kwargs)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\api.py", line 60, in request
    return session.request(method=method, url=url, **kwargs)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\sessions.py", line 533, in request
    resp = self.send(prep, **send_kwargs)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\sessions.py", line 646, in send
    r = adapter.send(request, **kwargs)
  File "D:\git_res\autotest\requests_easy\venv\lib\site-packages\requests\adapters.py", line 529, in send
    raise ReadTimeout(e, request=request)
requests.exceptions.ReadTimeout: HTTPConnectionPool(host='httpbin.org', port=80): Read timed out. (read timeout=0.35)

Process finished with exit code 1

可以看到，若在读取阶段超时，会抛出requests.exceptions.ReadTimeout异常。
2.元组传入
元组方式是对单值方式的一种细化，能够分别针对连接和读取阶段设置超时时间。如timeout=(0.3, 0.1),元组内第一个值为连接超时时间，第二个值为读取超时时间:

import requests

if __name__ == '__main__':
    r = requests.post("http://httpbin.org/post", timeout=(0.3, 0.1))

requests在连接阶段若超出连接超时时间，将抛出requests.exceptions.ConnectTimeout异常；requests在读取阶段若超出读取超时时间，将抛出requests.exceptions.ReadTimeout异常。

3.None
默认的传入方式。当不设置timeout参数，或者指定timeout=None，request将不限制超时时间，直到服务器响应数据，requests会持续等待。传入方式：

import requests

if __name__ == '__main__':
    r = requests.post("http://httpbin.org/post", timeout=None)