我在Linux下使用pip安裝時出現報錯：

Exception:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 215, in main
    status = self.run(options, args)
  File "/usr/lib/python2.7/dist-packages/pip/commands/install.py", line 353, in run
    wb.build(autobuilding=True)
  File "/usr/lib/python2.7/dist-packages/pip/wheel.py"
 
, line 749, in build
    self.requirement_set.prepare_files(self.finder)
  File "/usr/lib/python2.7/dist-packages/pip/req/req_set.py", line 380, in prepare_files
    ignore_dependencies=self.ignore_dependencies))
  File "/usr/lib/python2.7/dist-packages/pip/req/req_set.py", line 554, in _prepare_file
    require_hashes
  File "/usr/lib/python2.7/dist-packages/pip/req/req_install.py"
 
, line 278, in populate_link
    self.link = finder.find_requirement(self, upgrade)
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 465, in find_requirement
    all_candidates = self.find_all_candidates(req.name)
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 423, in find_all_candidates
    for
 
 page in self._get_pages(url_locations, project_name):
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 568, in _get_pages
    page = self._get_page(location)
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 683, in _get_page
    return HTMLPage.get_page(link, session=self.session)
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 792, in get_page
    "Cache-Control": "max-age=600",
  File "/usr/share/python-wheels/requests-2.12.4-py2.py3-none-any.whl/requests/sessions.py", line 501, in get
    return self.request('GET', url, **kwargs)
  File "/usr/lib/python2.7/dist-packages/pip/download.py", line 386, in request
    return super(PipSession, self).request(method, url, *args, **kwargs)
  File "/usr/share/python-wheels/requests-2.12.4-py2.py3-none-any.whl/requests/sessions.py", line 488, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/share/python-wheels/requests-2.12.4-py2.py3-none-any.whl/requests/sessions.py", line 609, in send
    r = adapter.send(request, **kwargs)
  File "/usr/share/python-wheels/CacheControl-0.11.7-py2.py3-none-any.whl/cachecontrol/adapter.py", line 47, in send
    resp = super(CacheControlAdapter, self).send(request, **kw)
  File "/usr/share/python-wheels/requests-2.12.4-py2.py3-none-any.whl/requests/adapters.py", line 423, in send
    timeout=timeout
  File "/usr/share/python-wheels/urllib3-1.19.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 643, in urlopen
    _stacktrace=sys.exc_info()[2])
  File "/usr/share/python-wheels/urllib3-1.19.1-py2.py3-none-any.whl/urllib3/util/retry.py", line 315, in increment
    total -= 1
TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'

錯誤的解決方法

網上有一個錯誤的解決方案

pip install --upgrade pip

執行這個命令後，進行pip安裝會報另外一個錯：

Traceback (most recent call last):
  File "/usr/bin/pip", line 9, in <module>
    from pip import main
ImportError: cannot import name main

解決方法是重新安裝pip，如：

python -m pip uninstall pip && sudo apt install python-pip --reinstall

或者可以修改/usr/bin/pip檔案，
把

from pip import main

改為

from pip._internal import main

正確的解決方案

使用如下命令

python -m pip install --upgrade pip
python -m pip install xxx