python pip安装requests时报错，怎么解决

D:\Python>pip install --allow-all-external requests
DEPRECATION: --allow-all-external has been deprecated and will be removed in the future. Due to changes in the repository protocol, it no longer has any effect.
Collecting requests
Downloading requests-2.12.4-py2.py3-none-any.whl (576kB)
39% |████████████▌ | 225kB 6.1kB/s eta 0:00:58Exception:
Traceback (most recent call last):
File "d:\python\lib\site-packages\pip\_vendor\requests\packages\urllib3\response.py", line 232, in _error_catcher
yield
File "d:\python\lib\site-packages\pip\_vendor\requests\packages\urllib3\response.py", line 314, in read
data = self._fp.read(amt)
File "d:\python\lib\site-packages\pip\_vendor\cachecontrol\filewrapper.py", line 60, in read
data = self.__fp.read(amt)
File "d:\python\lib\http\client.py", line 449, in read
n = self.readinto(b)
File "d:\python\lib\http\client.py", line 493, in readinto
n = self.fp.readinto(b)
File "d:\python\lib\socket.py", line 586, in readinto
return self._sock.recv_into(b)
File "d:\python\lib\ssl.py", line 1002, in recv_into
return self.read(nbytes, buffer)
File "d:\python\lib\ssl.py", line 865, in read
return self._sslobj.read(len, buffer)
File "d:\python\lib\ssl.py", line 625, in read
v = self._sslobj.read(len, buffer)
socket.timeout: The read operation timed out

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "d:\python\lib\site-packages\pip\basecommand.py", line 215, in main
status = self.run(options, args)
File "d:\python\lib\site-packages\pip\commands\install.py", line 324, in run
requirement_set.prepare_files(finder)
File "d:\python\lib\site-packages\pip\req\req_set.py", line 380, in prepare_files
ignore_dependencies=self.ignore_dependencies))
File "d:\python\lib\site-packages\pip\req\req_set.py", line 620, in _prepare_file
session=self.session, hashes=hashes)
File "d:\python\lib\site-packages\pip\download.py", line 821, in unpack_url
hashes=hashes
File "d:\python\lib\site-packages\pip\download.py", line 659, in unpack_http_url
hashes)
File "d:\python\lib\site-packages\pip\download.py", line 882, in _download_http_url
_download_url(resp, link, content_file, hashes)
File "d:\python\lib\site-packages\pip\download.py", line 603, in _download_url
hashes.check_against_chunks(downloaded_chunks)
File "d:\python\lib\site-packages\pip\utils\hashes.py", line 46, in check_against_chunks
for chunk in chunks:
File "d:\python\lib\site-packages\pip\download.py", line 571, in written_chunks
for chunk in chunks:
File "d:\python\lib\site-packages\pip\utils\ui.py", line 139, in iter
for x in it:
File "d:\python\lib\site-packages\pip\download.py", line 560, in resp_read
decode_content=False):
File "d:\python\lib\site-packages\pip\_vendor\requests\packages\urllib3\response.py", line 357, in stream
data = self.read(amt=amt, decode_content=decode_content)
File "d:\python\lib\site-packages\pip\_vendor\requests\packages\urllib3\response.py", line 324, in read
flush_decoder = True
File "d:\python\lib\contextlib.py", line 100, in __exit__
self.gen.throw(type, value, traceback)
File "d:\python\lib\site-packages\pip\_vendor\requests\packages\urllib3\response.py", line 237, in _error_catcher
raise ReadTimeoutError(self._pool, None, 'Read timed out.')
pip._vendor.requests.packages.urllib3.exceptions.ReadTimeoutError: HTTPSConnectionPool(host='pypi.python.org', port=443): Read timed out.

换一个国内的更新源吧：

pip install requests -i http://pypi.douban.com/simple --trusted-host=pypi.douban.com