virtualenv Getting started with virtualenv Installation or Setup

Example

Virtual Environment tool (virtualenv) is used to isolate different projects and their dependencies by creating individual python environments for each of them. It's like installing a package locally (and not globally), similar to npm package installation option. Following is an example to install and test virtualenv for creating two projects (Project1-A Django application and Project2- A Flask application):

1. Initially check if virtualenv is already installed $ virtualenv --version
2. Run $ pip install virtualenv (for Mac and Linux) or $ sudo apt-get install python-virtualenv for Ubuntu, easy_install for Windows to install the python environment.
3. $ mkdir Project1 and $ cd Project1
4. Run $ virtualenv venvp1 and this would create a venvp1 folder inside Project1 directory.
5. To activate the environment run source venvp1/bin/activate (if Linux) and venvp1\Scripts\activate (if Windows) and prompt will change to (venvp1)Your-Computer:your_project UserName$)
6. Run pip install Django to install Django for project1 and deactivate (if needed) to return to the global environment.
7. Repeat steps 3-6 for Flask application with different directory, virtualenv names and pip install Flask to install Flask.

Once above steps are executed (without any errors) one could (possibly and) simultaneously work between both environments without any conflicts.

Notes:

1. virtualenvwrapper is another handy tool which is extended version of virtualenv, though the installation procedure for both is nearly same.
2. Executing virtualenv command with --no-site-packages excludes the globally installed packages.
3. To freeze current state of environment run $ pip freeze > installedpkgp1.txt. This text file contains list of installed packages (including their versions) in the current environment. If there comes a need to deploy same environment at different folder (or machine) simply executing the command $ pip install -r installedpkgp1.txt would create same environment.
4. Useful commands:

• lsvirtualenv - list of all environments
• cdvirtualenv - goto currently activated virtual environment
• cdsitepackages - like previous, but goes directly to site-packages directory
• lssitepackages - shows content of site-packages directory