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An API for virtualenv/pip

Project description

Build Status Latest version BSD License

virtualenv is a tool to create isolated Python environments. Unfortunately, it does not expose a native Python API. This package aims to provide an API in the form of a wrapper around virtualenv.

It can be used to create and delete environments and perform package management inside the environment.

Full support is provided for all supported versions of Python.


The latest stable release is available on PyPi:

$ pip install virtualenv-api

Please note that the distribution is named virtualenv-api, yet the Python package is named virtualenvapi.

Alternatively, you may fetch the latest version from git:

$ pip install git+


To begin managing an environment (it will be created if it does not exist):

from virtualenvapi.manage import VirtualEnvironment
env = VirtualEnvironment('/path/to/environment/name')

If you have already activated a virtualenv and wish to operate on it, simply call VirtualEnvironment without the path argument:

env = VirtualEnvironment()

The VirtualEnvironment constructor takes some optional arguments (their defaults are shown below):

  • python=None - specify the Python interpreter to use. Defaults to the default system interpreter (new in 2.1.3)

  • cache=None - existing directory to override the default pip download cache

  • readonly=False - prevent all operations that could potentially modify the environment (new in 2.1.7)

  • system_site_packages=False - include system site packages in operations on the environment (new in 2.1.14)


Once you have a VirtualEnvironment object, you can perform operations on it.

  • Check if the mezzanine package is installed:

>>> env.is_installed('mezzanine')
  • Install the latest version of the mezzanine package:

>>> env.install('mezzanine')
  • A wheel of the latest version of the mezzanine package (new in 2.1.4):

>>> env.wheel('mezzanine')
  • Install version 1.4 of the django package (this is pip’s syntax):

>>> env.install('django==1.4')
  • Upgrade the django package to the latest version:

>>> env.upgrade('django')
  • Upgrade all packages to their latest versions (new in 2.1.7):

>>> env.upgrade_all()
  • Uninstall the mezzanine package:

>>> env.uninstall('mezzanine')

Packages may be specified as name only (to work on the latest version), using pip’s package syntax (e.g. django==1.4) or as a tuple of ('name', 'ver') (e.g. ('django', '1.4')).

  • A package may be installed directly from a git repository (must end with .git):

>>> env.install('git+git://')

New in 2.1.10:

  • A package can be installed in pip’s editable mode by prefixing the package name with -e (this is pip’s syntax):

>>> env.install('-e git+')

New in 2.1.15:

  • Packages in a pip requirements file can be installed by prefixing the requirements file path with -r:

>>> env.install('-r requirements.txt')
  • Instances of the environment provide an installed_packages property:

>>> env.installed_packages
[('django', '1.5'), ('wsgiref', '0.1.2')]
  • A list of package names is also available in the same manner:

>>> env.installed_package_names
['django', 'wsgiref']
  • Search for a package on PyPI (changed in 2.1.5: this now returns a dictionary instead of list):

{'virtualenv-api': 'An API for virtualenv/pip'}
>>> len('requests'))
  • The old functionality (pre 2.1.5) of may be used:

>>> list('requests').items())
[('virtualenv-api', 'An API for virtualenv/pip')]

Verbose output from each command is available in the environment’s build.log file, which is appended to with each operation. Any errors are logged to build.err.

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