What's the difference between "pip install" and "python -m pip install"?

Question

I have a local version of Python 3.4.1 and I can run python -m pip install, but I'm unable to find the pip binary to run pip install. What's the difference between these two?

Answer 1

They do exactly the same thing. In fact, the docs for distributing Python modules were just updated to suggest using python -m pip instead of the pip executable, because it's easier to tell which version of python is going to be used to actually run pip that way.

---

Here's some more concrete "proof", beyond just trusting my word and the bug report I linked :)

If you take a look at the pip executable script, it's just doing this:

from pkg_resources import load_entry_point
<snip>
load_entry_point('pip==1.5.4', 'console_scripts', 'pip')()

It's calling load_entry_point, which returns a function, and then executing that function. The entry point it's using is called 'console_scripts'. If you look at the entry_points.txt file for pip (/usr/lib/python2.7/dist-packages/pip-1.5.4.egg-info/entry_points.txt on my Ubuntu machine), you'll see this:

[console_scripts]
pip = pip:main
pip2.7 = pip:main
pip2 = pip:main

So the entry point returned is the main function in the pip module.

When you run python -m pip, you're executing the __main__.py script inside the pip package. That looks like this:

import sys
from .runner import run

if __name__ == '__main__':
    exit = run()
    if exit:
        sys.exit(exit)

And the runner.run function looks like this:

def run():
    base = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
    ## FIXME: this is kind of crude; if we could create a fake pip
    ## module, then exec into it and update pip.__path__ properly, we
    ## wouldn't have to update sys.path:
    sys.path.insert(0, base)
    import pip
    return pip.main()

As you can see, it's just calling the pip.main function, too. So both commands end up calling the same main function in pip/__init__.py.

Answer 2

2021

This only happens if you create the venv with PyCharm. Please check if Scripts/pip-script.py located in your virtual environment

pip install and python -m pip install -- is not really the same. Or welcome back into the HELL of VERSIONING & DEPENDENCIES :-(

I was used to type pip(.exe) install <name> if I want install a package. But I run into trouble, if I try to install package Pillow. It breaks every time with an error message.

Today I retry python -m pip install copy&pasted from the manual and it works. Before I ignored it and type pip.... Because I thought it is the same.

I start to dive a little bit deeper into pip and I find this question/answer. After a while I found that pip.exe calls the script <virtual-environment/Scripts>pip-script.py.

I fighting with the installation of package Pillow.

#! .\venv\Scripts\python.exe
# EASY-INSTALL-ENTRY-SCRIPT: 'pip==19.0.3','console_scripts','pip3'
__requires__ = 'pip==19.0.3'
import re
import sys
from pkg_resources import load_entry_point

if __name__ == '__main__':
    sys.argv[0] = re.sub(r'(-script\.pyw?|\.exe)?$', '', sys.argv[0])
    sys.exit(
        load_entry_point('pip==19.0.3', 'console_scripts', 'pip3')()
    )

I was a little bit surprised that pip.exe still use the old version 19.0.3 of the package and not the new installed version 21.0.1.

I changed the two version strings by hand to 21.0.1. And now pip.exe was able to install Pillow proper.

From now I understand why pip still complains that I use an old version of pip.

I think the old v19 pip has problem to detect the supported platform and therefore sources instead of binaries are installed.

Answer 3

Every installation of Python potentially comes with its own version of Pip. (Some installations may deliberately exclude Pip for security reasons: for example, when Python is included in a Linux distribution, it commonly omits Pip so that the user will not inadvertently install something harmful into a copy of Python that the operating system depends on.)

Conceptually, Pip consists of two pieces: the pip standard library module, contained in a pip.py file; and a pip "wrapper" executable. (On Windows this is implemented as an actual .exe file; on Mac and Linux, it should simply be a Python script that has execution privileges set and which does not have a .py filename extension.) The purpose of the wrapper is to run the "main" code in the corresponding standard library module.

Using pip at the command line will find and run whichever wrapper executable is first in the PATH environment variable, which will then run the corresponding Python code for the installation of Python associated with that wrapper. Therefore, it will install third-party libraries for whichever Python that is.

Using python -m pip at the command line will find and run whichever Python is first in the PATH environment variable, and instruct it to find the pip standard library module in its standard library (not directly; it will search sys.path just like with any module import) and run it "as a module". Therefore, it will install third-party libraries for the Python that was found in the PATH.

On Windows, using py -m pip at the command line will (unless the system is badly misconfigured) find and run the py executable, which is installed to a Windows directory that will always be on the PATH. This, in turn, will use its own logic to choose a Python on the system, run its pip, and from there it proceeds as before.

Depending on how the system is configured, these commands might not all choose the same Python installation.

Using python -m pip ensures that libraries are installed for the same Python that would run, using python myscript.py. This is very useful for those who are writing myscript.py, need that code to use the library that will be installed, and want it to run with whichever python that is.

As a special note for Windows, pip install --upgrade pip will not work. This is because upgrading Pip involves replacing the Pip wrapper executable on disk; by running the command this way, that wrapper executable is the program that is running, and Windows disallows programs from replacing themselves on disk. By using python -m pip install --upgrade pip, or py -m pip install --upgrade pip instead, the problem is avoided, because now the wrapper executable does not run - Python (and possibly also py) runs, using code from the pip.py (or a cached pip.pyc) file.