python install all dependencies from .py file code example

Example 1: how to install requirements file in python

pip install -r requirements.txt

Example 2: pip install python 3

You cannot just pip install python3 because it is not a library.

If you want to install the latest python3:
https://www.python.org/ftp/python/3.8.2/python-3.8.2.exe

Example 3: pip3 install requirements.txt

$ pip install -r requirements.txt --no-index --find-links file:///tmp/packages