Python Virtual environment
This page describe how to set virtual environment in Windows/Ubuntu.
Step by step
1. Install virtualenv
python3.7 -m pip install virtualenv
2. Make virtual env.
python3.7 -m virtualenv `venv-folder-name`
3. Activate Virtualenv
change directory into venv-folder-name(in example, “githubio”) and type activate.
# change directory
cd githubio
# Ubuntu
$ source bin/activate
# Windows
call scripts\activate
If activated successfully, (venv-folder-name) is shown at front of command. (in example, (githubio)). 
It’s better to double check python version typing like
python -V
Disable virutal environment
To deactivate, just type deactivate
Tips
Also, you could specify python version like belows.
(mind you should install wanted-python-version in advance.)
# python3.6
python3 -m virtualenv venv
virtualenv venv --python=python3.6
