install pip dependencies from file code example

Example 1: pip install from requirements.txt

$ pip install -r requirements.txt

Example 2: pip freeze requirements.txt

$ env1/bin/pip freeze > requirements.txt
$ env2/bin/pip install -r requirements.txt

Example 3: install requirements.txt in pip command

note: yor should be on the same dir as requirements.txt file 

pip install -r requirements.txt

Example 4: pip3 install requirements.txt

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