activate venv with pip code example

Example 1: python virtual environment

python3 -m venv env
python -m virtualenv env #py2

source env/bin/activate

#all this is on same directory

Example 2: how to create a new virtualenv

to make a new virtualenv: 
virtualenv env_name

             to activate this virtual environment:
source env_name/bin/activate (on mac and linux)
source env_name/Scripts/activate (on windows)