This extension just up to date all your python packages and requirements.txt file by calling only command in a new terminal or an existing one.
Press cmd+shift+p in mac or ctrl+shift+p in windows or linux and start typing update python ...
Following script will run:
for i in $(pip list -o | awk 'NR > 2 {print $1}'); do pip install -U $i; done && pip freeze > requirements.txt