Virtual Environments
====================
A Virtual Environment, put simply, is an isolated working copy of Python which
allows you to work on a specific project without worry of affecting other
projects.
For example, you can work on a project which requires Django 1.3 while also
maintaining a project which requires Django 1.0.
virtualenv
----------
`virtualenv `_ is a tool to create
isolated Python environments.
Install it via pip:
.. code-block:: console
$ pip install virtualenv
Basic Usage
~~~~~~~~~~~
1. Create a virtual environment:
.. code-block:: console
$ virtualenv venv
This creates a copy of Python in whichever directory you ran the command in,
placing it in a folder named ``venv``.
2. To begin using the virtual environment, it needs to be activated:
.. code-block:: console
$ source venv/bin/activate
You can then begin installing any new modules without affecting the system
default Python or other virtual environments.
3. If you are done working in the virtual environment for the moment, you can
deactivate it:
.. code-block:: console
$ deactivate
This puts you back to the system's default Python interpreter with all its
installed libraries.
To delete a virtual environment, just delete its folder.
After a while, though, you might end up with a lot of virtual environments
littered across your system, and its possible you'll forget their names or
where they were placed.
virtualenvwrapper
-----------------
`virtualenvwrapper `_
provides a set of commands which makes working with virtual environments much
more pleasant. It also places all your virtual environments in one place.
To install (make sure **virtualenv** is already installed):
.. code-block:: console
$ pip install virtualenvwrapper
$ export WORKON_HOME=~/Envs
$ source /usr/local/bin/virtualenvwrapper.sh
(`Full virtualenvwrapper install instructions `_.)
For Windows, you can use the `virtualenvwrapper-powershell `_ clone.
To install (make sure **virtualenv** is already installed):
.. code-block:: console
PS> pip install virtualenvwrapper-powershell
PS> $env:WORKON_HOME="~/Envs"
PS> mkdir $env:WORKON_HOME
PS> import-module virtualenvwrapper
Basic Usage
~~~~~~~~~~~
1. Create a virtual environment:
.. code-block:: console
$ mkvirtualenv venv
This creates the ``venv`` folder inside ``~/Envs``.
2. Work on a virtual environment:
.. code-block:: console
$ workon venv
**virtualenvwrapper** provides tab-completion on environment names. It really
helps when you have a lot of environments and have trouble remembering their
names.
``workon`` also deactivates whatever environment you are currently in, so you
can quickly switch between environments.
3. Deactivating is still the same:
.. code-block:: console
$ deactivate
4. To delete:
.. code-block:: console
$ rmvirtualenv venv
Other useful commands
~~~~~~~~~~~~~~~~~~~~~
``lsvirtualenv``
List all of the environments.
``cdvirtualenv``
Navigate into the directory of the currently activated virtual environment,
so you can browse its ``site-packages``, for example.
``cdsitepackages``
Like the above, but directly into ``site-packages`` directory.
``lssitepackages``
Shows contents of ``site-packages`` directory.
`Full list of virtualenvwrapper commands `_.
autoenv
-------
When you ``cd`` into a directory containing a ``.env`` `autoenv `_
automagically activates the environment.
Install it on Mac OS X using ``brew``:
.. code-block:: console
$ brew install autoenv
And on Linux:
.. code-block:: console
$ git clone git://github.com/kennethreitz/autoenv.git ~/.autoenv
$ echo 'source ~/.autoenv/activate.sh' >> ~/.bashrc