问题
I recently used pip to install the requests package in python 2.7, however in order to do so I had to use:
python -m pip install requests
instead of just:
python pip install requests
which gave me an error:
can't open file 'pip: [Errno 2] No such file or directory
Why did I need to add the -m?
回答1:
python -m pip tells python to run with the pip module as the main module.
python pip isn't understood, because pip isn't a command line argument that python understands (i.e., pip is a module).
If the python scripts directory (c:\python27\scripts for python 2.7 on windows) is on your path, then you can just run pip (without python before it) and pass the same options you would pass to python -m pip.
So: you need to add -m pip so python knows what module to use as the main module. pip is a standalone program installed in your python scripts directory, not an argument to python.
来源：https://stackoverflow.com/questions/40392499/why-is-m-needed-for-python-m-pip-install