Answers for "requirements.txt *"

pip install from requirements.txt

$ pip install -r requirements.txt

python requirements.txt

pip freeze #view requirements to be created (best done in virtual env)
pip freeze > requirements.txt #create requirements.txt (best done in virtual env)
pip install -r requirements.txt #install requirements.txt (best done in virtual env)

install requirements.txt in pip command

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

pip install -r requirements.txt