Answers for "how to use virtual env in another file"

python create virtualenv

pip install virtualenv # install first
cd projectfolder # go to project folder
python -m venv ./venv # Create a virtual environment named venv
Activate.ps1 # (powershell) start the file  to start the environment
activate.bat # (cmd) start the file  to start the environment
# if it worked you'll see a (venv) in front of your cursor path

python virtual env

$ virtualenv -p /usr/bin/python2.7 venv