Installation virtualenv, create a python virtual environment.
1) Installation virtualenv: pip install virtualenv // virtualenv -version check for correct installation.
2) Create a python virtual environment: virtualenv venv // cd to the directory under the file you want to go to, and the name of the environment depend on your hobby.
3) Start the virtual environment: activate // cd to perform a virtual environment scripts directory Folder
4) exit the virtual environment: deactivate // cd to perform a virtual environment directory folder scripts.
Of course, you can also specify the required version of python, execute the command:
virtualenv Venv -python = python3.4.0
(provided that the python3.4.0 installed on your machine)