*virtualenv* is a tool used to create an isolated workspace for a [Python](/index.php/Python "Python") application. It has various advantages such as the ability to install modules locally, export a working environment, and execute a [Python](/index.php/Python "Python") program in that environment. ## Contents * [1 Overview](#Overview) * [2 Installation](#Installation) * [2.1 Packages](#Packages) * [3 Usage](#Usage) * [3.1 Creation](#Creation) * [3.1.1 venv](#venv) * [3.1.2 virtualenv](#virtualenv) * [3.2 Activation](#Activation) * [4 Python versions](#Python_versions) * [5 virtualenvwrapper](#virtualenvwrapper) * [5.1 Installation](#Installation_2) * [5.2 Basic usage](#Basic_usage) * [6 See also](#See_also) ## Overview A virtual environment is a directory into which some binaries and shell scripts are installed. The binaries include *python* for executing scripts and *pip* for installing other modules within the environment. There are also shell scripts (one for [bash](/index.php/Bash "Bash"), csh, and [fish](/index.php/Fish "Fish")) to activate the environment. Essentially, a virtual environment mimics a full system install of [Python](/index.php/Python "Python") and all of the desired modules without interfering with any system on which the application might run. ## Installation [Python](/index.php/Python "Python") 3.3+ comes with a module called *venv*. For applications that require an older version of Python, *virtualenv* must be used. ### Packages [Install](/index.php/Install "Install") one of these packages from the [official repositories](/index.php/Official_repositories "Official repositories") to use a Python virtual environment. * Python 3.3+: [python](https://www.archlinux.org/packages/?name=python) * Python 3: [python-virtualenv](https://www.archlinux.org/packages/?name=python-virtualenv) * Python 2: [python2-virtualenv](https://www.archlinux.org/packages/?name=python2-virtualenv) ## Usage All three tools use a similar workflow. ### Creation Use *venv* or *virtualenv* to create the virtual environment within your project directory. Be sure to exclude the venv directory from version control--a copy of `pip freeze` will be enough to rebuild it. #### venv **Note:** This method replaces the *pyvenv* script, which is deprecated since [python](https://www.archlinux.org/packages/?name=python) 3.6. This tool is provided by [python](https://www.archlinux.org/packages/?name=python) (3.3+): ``` $ python -m venv venv ``` #### virtualenv Use *virtualenv* for Python 3, available in [python-virtualenv](https://www.archlinux.org/packages/?name=python-virtualenv). ``` $ virtualenv venv ``` And *virtualenv2* for Python 2, available in [python2-virtualenv](https://www.archlinux.org/packages/?name=python2-virtualenv). ``` $ virtualenv2 venv ``` ### Activation Use one of the provided shell scripts to activate and deactivate the environment. This example assumes bash is used. ``` $ source venv/bin/activate (venv) $ ``` Once inside the virtual environment, modules can be installed with *pip* and scripts can be run as normal. To exit the virtual environment, run the function provided by `bin/activate`: ``` (venv) $ deactivate ``` ## Python versions The binary versions depend on which virtual environment tool was used. For instance, the *python* command used in the Python 2 example points to `bin/python2.7`, while the one in the *venv* example points to `bin/python3.6`. One major difference between *venv* and *virtualenv* is that the former uses the system's Python binary by default: ``` $ ls -l venv/bin/python3.6 lrwxrwxrwx 1 foo foo 7 Jun 3 19:57 venv/bin/python3.6 -> /usr/bin/python3 ``` The *virtualenv* tool uses a separate Python binary in the environment directory: ``` $ ls -l virtualenv/bin/python3.6 lrwxrwxrwx 1 foo foo 7 Jun 3 19:58 virtualenv/bin/python3.6 -> python3 ``` ## virtualenvwrapper *virtualenvwrapper* allows more natural command line interaction with your virtual environemnts by exposing several useful commands to create, activate and remove virtual environments. This package is a wrapper for both [python-virtualenv](https://www.archlinux.org/packages/?name=python-virtualenv) and [python2-virtualenv](https://www.archlinux.org/packages/?name=python2-virtualenv). ### Installation [Install](/index.php/Install "Install") the [python-virtualenvwrapper](https://www.archlinux.org/packages/?name=python-virtualenvwrapper) package from the [official repositories](/index.php/Official_repositories "Official repositories"). Now add the following lines to your `~/.bashrc`: ``` export WORKON_HOME=~/.virtualenvs source /usr/bin/virtualenvwrapper.sh ``` Since python3 is a system-wide default in Arch, in order to be able to create python2 environments, you need to set `VIRTUALENVWRAPPER_PYTHON` and `VIRTUALENVWRAPPER_VIRTUALENV` prior to sourcing `virtualenvwrapper.sh` in your `~/.bashrc`: ``` export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python2.7 export VIRTUALENVWRAPPER_VIRTUALENV=/usr/bin/virtualenv2 ``` The line `source /usr/bin/virtualenvwrapper.sh` can cause some slowdown when starting a new shell. To fix this try using `source /usr/bin/virtualenvwrapper_lazy.sh`, which will load virtualenvwrapper the first time a virtualenvwrapper function is called. If you are not using python3 by default (check the output of `python --version`) you need to add the following line to your `~/.bashrc` prior sourcing the `virtualenvwrapper.sh` script. ``` export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3 ``` Re-open your console and create the `WORKON_HOME` folder: ``` $ mkdir $WORKON_HOME ``` **Note:** This seems to happen now automatically after re-open the console for the first time. ### Basic usage The main information source on virtualenvwrapper usage (and extension capability) is Doug Hellmann's [page](http://www.doughellmann.com/docs/virtualenvwrapper/). Create the virtual environment: ``` $ mkvirtualenv -p /usr/bin/python2.7 my_env ``` Activate the virtual environment: ``` $ workon my_env ``` Install some package inside the virtual environment (say, Django): ``` (my_env) $ pip install django ``` After you have done your things, leave the virtual environment: ``` (my_env) $ deactivate ``` ## See also * [Python venv](https://docs.python.org/3/library/venv.html) * [virtualenv PyPI page](https://pypi.org/project/virtualenv/) * [virtualenvwrapper page at Doug Hellmann's](http://www.doughellmann.com/docs/virtualenvwrapper/)