Virtual environment in python

VirtualEnv.md

Virutal environment is an useful utility for python to install packages locally and not globally so your system remains clean after installing multiples packages. It is recommended to avoid future conflicts between packages.

To install virtual environment you just have to type:

$ pip install virtualenv

To check the installation:

$ virtualenv --version

To create a virtual environment for a project:

$ cd projectFolder
$ virtualenv projectName

Now you can see what virtualenv has installed in the projectFolder. Basically, it has created a subfolder named projectName and inside it you locate the next folders:

bin include lib local man share 

In the bin folder a copy of your pip binary has been created which will manage future installations in this local environment. You can also specify the python interpreter to be used on this virtual enviroment. There are two ways to define the interpreter:

1st method  -> $ virtualenv -p /usr/local/pyton3 projectName
2nd method  -> $ echo 'export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3' >> ~/.bashrc

In the second method you are setting the python interpreter globally.

To activate the virtual environment, you must type:

  $ source projectFolder/bin/activate

To deactivate you only must type:

  $ deactivate

Once you have activated the environment you can now install all the packages required for your project and they will be installed locally within your project folder instead of your system.

Virtualenvwrapper

This other utility to manage your virtual environments which offers more control. To install it, you must have previously installed virtualenv.

  $ pip search virtualenv
        virtualenv (15.1.0)                      - Virtual Python Environment builder
        INSTALLED: 15.1.0 (latest)

  $ sudo pip install virtualenvwrapper
  $ mkdir ~/Envs
  $ export WORKON_HOME=~/Envs 
  $ source /usr/local/bin/virtualenvwrapper.sh

To export the WORKON_HOME variable and make it permanent, include it on your bashrc file:

  $ echo 'export WORKON_HOME=~/Envs' >> ~/.bashrc

BASIC USAGE

Create a virtual environment:

  $ mkvirtualenv projectName

It creates the projectName folder for the virtual environment inside ~/Envs directory.

Work on the virtual environment:

  $ workon projectName

There is an alternative to create the virtual environment but it also creates the project directory inside the $WORKON_HOME directory:

  $ mkproject projectName

Deactivate is the same as the virtualenv:

  $ deactivate

To remove the project from the $WORKON_HOME you must deactivate it and then:

  $ rmvirtualenv projectName

(To delete in the case of virtualenv you only have to delete recursively the entire folder where the project is located.)

Other useful commands for virtualenvwrapper:

List all the virtual environments:

  $ lsvirutalenv

Navigate into the directory of the currently activated virtual environment, so you can browse its site-packages, for example.

  $ cdvirtualenv

Like the above, but directly into site-packages directory.

  $ cdsitepackages

Shows contents of site-packages directory.

  $ lssitepackages      

Source

• http://docs.python-guide.org