On windows:

py -m venv venv
venv\Scripts\activate.bat
py -m pip install --upgrade pip
py -m pip install -r requirements.txt
py -m pip install --upgrade pytube

On mac/linux:

python3 -m venv venv
venv/bin/activate
python3 -m pip install --upgrade pip
python3 -m pip install -r requirements.txt
python3 -m pip install --upgrade pytube