virtualenv

virtualenv allows you to create isolated python environments. For example you can create an isolated environment in your project by navigating to the project folder and running virtualenv venv which will create a folder venv in your project containing a copy of python to be used in your virtual environment.

venv is a name used by convention, and is usually included in .gitignore files for example.

Using the virtualenv

To use a virtual environment after creating it, you can run the command

source venv/bin/activate

this will set your python interpreter to the one stored in your venv folder and any package installation you do (for example with pip) will be attributed to that environment.

Leaving a virtualenv

To leave a virtualenv you simply run

deactivate

Deleting a virtualenv

To delete a virtualenv, just delete the corresponding folder.

Running without global packages

The --no-site-packages flag stops the virtual environment from using globally installed packes. It is default behaviour for virtualenv 1.7+