which pip

    /usr/local/bin/pip

 pip

    -su: /usr/bin/pip: No such file or directory

    type pip

    pip is hashed (/usr/bin/pip)
    So pip is definintely in /usr/local/bin/pip but it is been cached as in /usr/bin/pip, thanks to the Stackoverflow question, the solution is very simple:
 

   hash -r

    When the cache is clear, pip is working again.

這樣之後在進行操作，就可以使用pip了。

原文：原文連結