virtualenvwrapper is a set of extensions to Ian Bicking’s virtualenv tool. The extensions include wrappers for creating and deleting virtual environments and otherwise managing your development workflow, making it easier to work on more than one project at a time without introducing conflicts in their dependencies.
Organizes all of your virtual environments in one place.
Wrappers for managing your virtual environments (create, delete, copy).
Use a single command to switch between environments.
Tab completion for commands that take a virtual environment as argument.
User-configurable hooks for all operations (see Per-User Customization).
Plugin system for creating more sharable extensions (see Extending Virtualenvwrapper).
This guide discusses how to install packages using pip and a virtual environment manager: either venv for Python 3 or virtualenv for Python 2. These are the lowest-level tools for managing Python packages and are recommended if higher-level tools do not suit your needs.
Well, a virtual environment is just a directory with three important components:
A site-packages/ folder where third party libraries are installed.
Symlinks to Python executables installed on your system.
Scripts that ensure executed Python code uses the Python interpreter and site packages installed inside the given virtual environment.
(venv) % pip freeze
And write the output to a file, which we’ll call requirements.txt.