How to install python virtualenv

1. install the package virtualenv

pip install virtualenv

2. create a virtualenv

virtualenv <name_of_your_virtualenv>

3. activate the created virtualenv

source path_to_your_virtualenv/bin/activate

4. “freeze” the current state of the environment packages of the other virtual_env:

 pip freeze > requirements.txt

5. install the packages in your new virtualenv:

 pip install -r requirements.txt