pip 說它已過時，但更新說它是最新版本！

如果我嘗試執行以下操作：

pip --version

我明白了：

Traceback (most recent call last):
 File "/usr/bin/pip", line 6, in <module>
   from pkg_resources import load_entry_point
 File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3049, in <module>
   @_call_aside
 File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3033, in _call_aside
   f(*args, **kwargs)
 File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3062, in _initialize_master_working_set
   working_set = WorkingSet._build_master()
 File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 660, in _build_master
   return cls._build_from_requirements(__requires__)
 File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 673, in _build_from_requirements
   dists = ws.resolve(reqs, Environment())
 File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 858, in resolve
   raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'pip==9.0.3' distribution was not found and is required by the application

看起來 pip 已經過時了，所以我嘗試這樣做：

python -m pip install --upgrade pip

我明白了：

Requirement already up-to-date: pip in /usr/local/lib/python2.7/site-packages (10.0.1)

所以我很困惑！如何讓 pip 達到 pip 似乎需要的版本？

有關安裝的更多資訊，whereis 告訴我 pip 可在此處獲得：

pip: /usr/bin/pip /usr/local/bin/pip /usr/local/bin/pip2.7

和蟒蛇：

python: /usr/bin/python2.6-config /usr/bin/python2.6 /usr/bin/python2.7-config /usr/bin/python2.7 /usr/bin/python /usr/lib/python2.6 /usr/lib/python2.7 /usr/lib64/python2.6 /usr/lib64/python2.7 /usr/local/lib/python2.6 /usr/local/lib/python2.7 /usr/include/python2.6 /usr/include/python2.7 /usr/share/man/man1/python.1.gz

正如@Kusalananda 所說，/usr/bin 和 /usr/local/bin 中有多個版本的 pip。我通過創建從 /usr/bin 到 /usr/local/bin 中最新版本的符號連結解決了這個問題：

sudo ln -s /usr/local/bin/pip /usr/bin/pip

您可以使用符號連結或使用最新的 pip 版本安裝應用程序/usr/local/bin/

引用自：https://unix.stackexchange.com/questions/449486