Sometimes you may need to use pip package manager inside python eg. when some imports may raise
ImportError and you want to handle the exception. If you unpack on Windows
Python_root/Scripts/pip.exeinside is stored
__main__.py file, where
main class from
pip package is imported. This means pip package is used whenever you use pip executable. For usage of pip as executable see: pip: PyPI Package Manager
import pip command = 'install' parameter = 'selenium' second_param = 'numpy' # You can give as many package names as needed switch = '--upgrade' pip.main([command, parameter, second_param, switch])
Only needed parameters are obligatory, so both
pip.main(['freeze', '', '']) are aceptable.
It is possible to pass many package names in one call, but if one install/upgrade fails, whole installation process stops and ends with status '1'.
import pip installed = pip.get_installed_distributions() list =  for i in installed: list.append(i.key) pip.main(['install']+list+['--upgrade'])
If you don't want to stop when some installs fail, call installation in loop.
for i in installed: pip.main(['install']+i.key+['--upgrade'])
When you use python file as module there is no need always check if package is installed but it is still useful for scripts.
if __name__ == '__main__': try: import requests except ImportError: print("To use this module you need 'requests' module") t = input('Install requests? y/n: ') if t == 'y': import pip pip.main(['install', 'requests']) import requests import os import sys pass else: import os import sys print('Some functionality can be unavailable.') else: import requests import os import sys
Many packages for example on version 3.4 would run on 3.6 just fine, but if there are no distributions for specific platform, they can't be installed, but there is workaround. In .whl files (known as wheels) naming convention decide whether you can install package on specified platform. Eg.
scikit_learn‑0.18.1‑cp36‑cp36m‑win_amd64.whl[package_name]-[version]-[python interpreter]-[python-interpreter]-[Operating System].whl. If name of wheel file is changed, so platform does match, pip tries to install package even if platform or python version does not match. Removing platform or interpreter from name will rise an error in newest versoin of pip module
kjhfkjdf.whl is not a valid wheel filename..
Alternativly .whl file can be unpacked using an archiver as 7-zip. - It usually contains distribution meta folder and folder with source files. These source files can be simply unpacked to
site-packges directory unless this wheel contain installation script, if so, it has to be run first.