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virtualenv is a tool to create isolated Python environments. Since Python 3.3, a subset of it has been integrated into the standard library under the venv module. The venv module does not offer all features of this library, to name just a few more prominent:

  • is slower (by not having the app-data seed method),
  • is not as extendable,
  • cannot create virtual environments for arbitrarily installed python versions (and automatically discover these),
  • is not upgrade-able via pip,
  • does not have as rich programmatic API (describe virtual environments without creating them).

The basic problem being addressed is one of dependencies and versions, and indirectly permissions. Imagine you have an application that needs version 1 of LibFoo, but another application requires version 2. How can you use both these libraries? If you install everything into your host python (e.g. python3.8) it's easy to end up in a situation where two packages have conflicting requirements.

Or more generally, what if you want to install an application and leave it be? If an application works, any change in its libraries or the versions of those libraries can break the application. Also, what if you can't install packages into the global site-packages directory, due to not having permissions to change the host python environment?

In all these cases, virtualenv can help you. It creates an environment that has its own installation directories, that doesn't share libraries with other virtualenv environments (and optionally doesn't access the globally installed libraries either).

Related projects, that build abstractions on top of virtualenv

  • virtualenvwrapper - a useful set of scripts for creating and deleting virtual environments
  • pew - provides a set of commands to manage multiple virtual environments
  • tox - a generic virtualenv management and test automation command line tool, driven by a tox.ini configuration file
  • nox - a tool that automates testing in multiple Python environments, similar to tox, driven by a configuration file


  • Corey Schafer tutorial on how to use it
  • Using virtualenv with mod_wsgi

Presenting how the package works from within

  • Bernat Gabor: status quo of virtual environments
  • Carl Meyer: Reverse-engineering Ian Bicking's brain: inside pip and virtualenv

virtualenv is a CLI tool that needs a Python interpreter to run. If you already have a Python 3.5+ interpreter the best is to use pipx to install virtualenv into an isolated environment. This has the added benefit that later you'll be able to upgrade virtualenv without affecting other parts of the system.

pipx install virtualenv
virtualenv --help

Alternatively you can install it within the global Python interpreter itself (perhaps as a user package via the --user flag). Be cautious if you are using a python install that is managed by your operating system or another package manager. pip might not coordinate with those tools, and may leave your system in an inconsistent state. Note, if you go down this path you need to ensure pip is new enough per the subsections below:

python -m pip install --user virtualenv
python -m virtualenv --help

Installing virtualenv via a wheel (default with pip) requires an installer that can understand the python-requires tag (see PEP-503), with pip this is version 9.0.0 (released 2016 November). Furthermore, in case you're not installing it via the PyPi you need to be using a mirror that correctly forwards the python-requires tag (notably the OpenStack mirrors don't do this, or older devpi versions - added with version 4.7.0).

When installing via a source distribution you need an installer that handles the PEP-517 specification. In case of pip this is version 18.0.0 or later (released on 2018 July). If you cannot upgrade your pip to support this you need to ensure that the build requirements from pyproject.toml are satisfied before triggering the install.

You can use virtualenv without installing it too. We publish a Python zipapp, you can just download this from and invoke this package with a python interpreter:

python virtualenv.pyz --help

The root level zipapp is always the current latest release. To get the last supported zipapp against a given python minor release use the link, e.g. for the last virtualenv supporting Python 2.7 use

If you are looking for past version of virtualenv.pyz they are available here:<virtualenv version>/public/<python version>/virtualenv.pyz?raw=true

We don't recommend and officially support this method. One should prefer using an installer that supports PEP-517 interface, such as pip 19.0.0 or later. That being said you might be able to still install a package via this method if you satisfy build dependencies before calling the install command (as described under sdist).

Installing an unreleased version is discouraged and should be only done for testing purposes. If you do so you'll need a pip version of at least 18.0.0 and use the following command:

pip install git+

virtualenv works with the following Python interpreter implementations:

  • CPython versions 2.7, 3.5, 3.6, 3.7, 3.8, 3.9, 3.10
  • PyPy 2.7 and 3.5+.

This means virtualenv works on the latest patch version of each of these minor versions. Previous patch versions are supported on a best effort approach.

CPython is shipped in multiple forms, and each OS repackages it, often applying some customization along the way. Therefore we cannot say universally that we support all platforms, but rather specify some we test against. In case of ones not specified here the support is unknown, though likely will work. If you find some cases please open a feature request on our issue tracker.

  • installations from
  • Ubuntu 16.04+ (both upstream and deadsnakes builds)
  • Fedora
  • RHEL and CentOS
  • OpenSuse
  • Arch Linux

In case of macOS we support:

  • installations from
  • python versions installed via brew (both older python2.7 and python3)
  • Python 3 part of XCode (Python framework - /Library/Frameworks/Python3.framework/)
  • Python 2 part of the OS (/System/Library/Frameworks/Python.framework/Versions/)

  • Installations from
  • Windows Store Python - note only version 3.7+

  • Normal variant (file structure as comes from
  • We support CPython 2 system installations that do not contain the python files for the standard library if the respective compiled files are present (e.g. only os.pyc, not This can be used by custom systems may want to maximize available storage or obfuscate source code by removing .py files.

Virtualenv has one basic command:

virtualenv venv

This will create a python virtual environment of the same version as virtualenv, installed into the subdirectory venv. The command line tool has quite a few of flags that modify the tool's behaviour, for a full list make sure to check out CLI flags.

The tool works in two phases:

  • Phase 1 discovers a python interpreter to create a virtual environment from (by default this is the same python as the one virtualenv is running from, however we can change this via the p option).
  • Phase 2 creates a virtual environment at the specified destination (dest), this can be broken down into four further sub-steps:
  • create a python that matches the target python interpreter from phase 1,
  • install (bootstrap) seed packages (one or more of pip, setuptools, wheel) in the created virtual environment,
  • install activation scripts into the binary directory of the virtual environment (these will allow end users to activate the virtual environment from various shells).
  • create files that mark the virtual environment as to be ignored by version control systems (currently we support Git only, as Mercurial, Bazaar or SVN do not support ignore files in subdirectories). This step can be skipped with the no-vcs-ignore option.

The python in your new virtualenv is effectively isolated from the python that was used to create it.

Python discovery

The first thing we need to be able to create a virtual environment is a python interpreter. This will describe to the tool what type of virtual environment you would like to create, think of it as: version, architecture, implementation.

virtualenv being a python application has always at least one such available, the one virtualenv itself is using, and as such this is the default discovered element. This means that if you install virtualenv under python 3.8, virtualenv will by default create virtual environments that are also of version 3.8.

Created python virtual environments are usually not self-contained. A complete python packaging is usually made up of thousands of files, so it's not efficient to install the entire python again into a new folder. Instead virtual environments are mere shells, that contain little within themselves, and borrow most from the system python (this is what you installed, when you installed python itself). This does mean that if you upgrade your system python your virtual environments might break, so watch out. The upside of this, referring to the system python, is that creating virtual environments can be fast.

Here we'll describe the built-in mechanism (note this can be extended though by plugins). The CLI flag p or python allows you to specify a python specifier for what type of virtual environment you would like, the format is either:

  • a relative/absolute path to a Python interpreter,
  • a specifier identifying the Python implementation, version, architecture in the following format:
{python implementation name}{version}{architecture}

We have the following restrictions:

  • the python implementation is all alphabetic characters (python means any implementation, and if is missing it defaults to python),
  • the version is a dot separated version number,
  • the architecture is either -64 or -32 (missing means any).

For example:

  • python3.8.1 means any python implementation having the version 3.8.1,
  • 3 means any python implementation having the major version 3,
  • cpython3 means a CPython implementation having the version 3,
  • pypy2 means a python interpreter with the PyPy implementation and major version 2.

Given the specifier virtualenv will apply the following strategy to discover/find the system executable:

  • If we're on Windows look into the Windows registry, and check if we see any registered Python implementations that match the specification. This is in line with expectation laid out inside PEP-514
  • Try to discover a matching python executable within the folders enumerated on the PATH environment variable. In this case we'll try to find an executable that has a name roughly similar to the specification (for exact logic, please see the implementation code).


As detailed above, virtual environments usually just borrow things from the system Python, they don't actually contain all the data from the system Python. The version of the python executable is hardcoded within the python exe itself. Therefore, if you upgrade your system Python, your virtual environment will still report the version before the upgrade, even though now other than the executable all additional content (standard library, binary libs, etc) are of the new version.

Barring any major incompatibilities (rarely the case) the virtual environment will continue working, but other than the content embedded within the python executable it will behave like the upgraded version. If such a virtual environment python is specified as the target python interpreter, we will create virtual environments that match the new system Python version, not the version reported by the virtual environment.

These are what actually setup the virtual environment, usually as a reference against the system python. virtualenv at the moment has two types of virtual environments:

  • venv - this delegates the creation process towards the venv module, as described in PEP 405. This is only available on Python interpreters having version 3.5 or later, and also has the downside that virtualenv must create a process to invoke that module (unless virtualenv is installed in the system python), which can be an expensive operation (especially true on Windows).
  • builtin - this means virtualenv is able to do the creation operation itself (by knowing exactly what files to create and what system files need to be referenced). The creator with name builtin is an alias on the first creator that's of this type (we provide creators for various target environments, that all differ in actual create operations, such as CPython 2 on Windows, PyPy2 on Windows, CPython3 on Posix, PyPy3 on Posix, and so on; for a full list see creator).

These will install for you some seed packages (one or more of: pip, setuptools, wheel) that enables you to install additional python packages into the created virtual environment (by invoking pip). There are two main seed mechanism available:

  • pip - this method uses the bundled pip with virtualenv to install the seed packages (note, a new child process needs to be created to do this, which can be expensive especially on Windows).
  • app-data - this method uses the user application data directory to create install images. These images are needed to be created only once, and subsequent virtual environments can just link/copy those images into their pure python library path (the site-packages folder). This allows all but the first virtual environment creation to be blazing fast (a pip mechanism takes usually 98% of the virtualenv creation time, so by creating this install image that we can just link into the virtual environments install directory we can achieve speedups of shaving the initial 1 minute and 10 seconds down to just 8 seconds in case of a copy, or 0.8 seconds in case symlinks are available - this is on Windows, Linux/macOS with symlinks this can be as low as 100ms from 3+ seconds). To override the filesystem location of the seed cache, one can use the VIRTUALENV_OVERRIDE_APP_DATA environment variable.

To install a seed package via either pip or app-data method virtualenv needs to acquire a wheel of the target package. These wheels may be acquired from multiple locations as follows:

  • virtualenv ships out of box with a set of embed wheels for all three seed packages (pip, setuptools, wheel). These are packaged together with the virtualenv source files, and only change upon upgrading virtualenv. Different Python versions require different versions of these, and because virtualenv supports a wide range of Python versions, the number of embedded wheels out of box is greater than 3. Whenever newer versions of these embedded packages are released upstream virtualenv project upgrades them, and does a new release. Therefore, upgrading virtualenv periodically will also upgrade the version of the seed packages.
  • However, end users might not be able to upgrade virtualenv at the same speed as we do new releases. Therefore, a user might request to upgrade the list of embedded wheels by invoking virtualenv with the upgrade-embed-wheels flag. If the operation is triggered in such a manual way subsequent runs of virtualenv will always use the upgraded embed wheels.

    The operation can trigger automatically too, as a background process upon invocation of virtualenv, if no such upgrade has been performed in the last 14 days. It will only start using automatically upgraded wheel if they have been released for more than 28 days, and the automatic upgrade finished at least an hour ago:

  • the 28 days period should guarantee end users are not pulling in automatically releases that have known bugs within,
  • the one hour period after the automatic upgrade finished is implemented so that continuous integration services do not start using a new embedded versions half way through.

The automatic behaviour might be disabled via the no-periodic-update configuration flag/option. To acquire the release date of a package virtualenv will perform the following:

  • lookup<distribution>/json (primary truth source),
  • save the date the version was first discovered, and wait until 28 days passed.
Users can specify a set of local paths containing additional wheels by using the extra-search-dir command line argument flag.

When searching for a wheel to use virtualenv performs lookup in the following order:

  • embedded wheels,
  • upgraded embedded wheels,
  • extra search dir.

Bundled wheels are all three above together. If neither of the locations contain the requested wheel version or download option is set will use pip download to load the latest version available from the index server.

Custom distributions often want to use their own set of wheel versions to distribute instead of the one virtualenv releases on PyPi. The reason for this is trying to keep the system versions of those packages in sync with what virtualenv uses. In such cases they should patch the module virtualenv.seed.wheels.embed, making sure to provide the function get_embed_wheel (which returns the wheel to use given a distribution/python version). The BUNDLE_FOLDER, BUNDLE_SUPPORT and MAX variables are needed if they want to use virtualenv's test suite to validate.

Furthermore, they might want to disable the periodic update by patching the virtualenv.seed.embed.base_embed.PERIODIC_UPDATE_ON_BY_DEFAULT to False, and letting the system update mechanism to handle this. Note in this case the user might still request an upgrade of the embedded wheels by invoking virtualenv via upgrade-embed-wheels, but no longer happens automatically, and will not alter the OS provided wheels.

These are activation scripts that will mangle with your shell's settings to ensure that commands from within the python virtual environment take priority over your system paths. For example, if invoking pip from your shell returned the system python's pip before activation, once you do the activation this should refer to the virtual environments pip. Note, though that all we do is change priority; so, if your virtual environments bin/Scripts folder does not contain some executable, this will still resolve to the same executable it would have resolved before the activation.

For a list of shells we provide activators see activators. The location of these is right alongside the python executables ( usually Scripts folder on Windows, bin on POSIX), and are named as activate (and some extension that's specific per activator; no extension is bash). You can invoke them, usually by source-ing (the source command might vary by shell - e.g. bash is .):

source bin/activate

This is all it does; it's purely a convenience of prepending the virtual environment's binary folder onto the PATH environment variable. Note you don't have to activate a virtual environment to use it. In this case though you would need to type out the path to the executables, rather than relying on your shell to resolve them to your virtual environment.

The activate script will also modify your shell prompt to indicate which environment is currently active. The script also provisions a deactivate command that will allow you to undo the operation:



If using Powershell, the activate script is subject to the execution policies on the system. By default, Windows 7 and later, the system's execution policy is set to Restricted, meaning no scripts like the activate script are allowed to be executed.

However, that can't stop us from changing that slightly to allow it to be executed. You may relax the system execution policy to allow running of local scripts without verifying the code signature using the following:

Set-ExecutionPolicy RemoteSigned

Since the activate.ps1 script is generated locally for each virtualenv, it is not considered a remote script and can then be executed.

A longer explanation of this can be found within Allison Kaptur's 2013 blog post: There's no magic: virtualenv edition explains how virtualenv uses bash and Python and PATH and PYTHONHOME to isolate virtual environments' paths.

At the moment virtualenv offers only CLI level interface. If you want to trigger invocation of Python environments from within Python you should be using the virtualenv.cli_run method; this takes an args argument where you can pass the options the same way you would from the command line. The run will return a session object containing data about the created virtual environment.

from virtualenv import cli_run
Create a virtual environment given some command line interface arguments.
  • args -- the command line arguments
  • options -- passing in a VirtualEnvOptions object allows return of the parsed options
  • setup_logging -- True if setup logging handlers, False to use handlers already registered
  • env -- environment variables to use
the session object of the creation (its structure for now is experimental and might change on short notice)
Create a virtualenv session (same as cli_run, but this does not perform the creation). Use this if you just want to query what the virtual environment would look like, but not actually create it.
  • args -- the command line arguments
  • options -- passing in a VirtualEnvOptions object allows return of the parsed options
  • setup_logging -- True if setup logging handlers, False to use handlers already registered
  • env -- environment variables to use
the session object of the creation (its structure for now is experimental and might change on short notice)
Represents a virtual environment creation session
The verbosity of the run
Create a virtual environment based on this reference interpreter
The creator used to build the virtual environment (must be compatible with the interpreter)
The mechanism used to provide the seed packages (pip, setuptools, wheel)
Activators used to generate activations scripts

virtualenv is primarily a command line application.

It modifies the environment variables in a shell to create an isolated Python environment, so you'll need to have a shell to run it. You can type in virtualenv (name of the application) followed by flags that control its behaviour. All options have sensible defaults, and there's one required argument: then name/path of the virtual environment to create. The default values for the command line options can be overridden via the Configuration file or Environment Variables. Environment variables takes priority over the configuration file values (--help will show if a default comes from the environment variable as the help message will end in this case with environment variables or the configuration file).

The options that can be passed to virtualenv, along with their default values and a short description are listed below.

virtualenv [OPTIONS]

display the version of the virtualenv package and its location, then exit
False on failure also display the stacktrace internals of virtualenv
False use app data folder in read-only mode (write operations will fail with error)
platform specific application data folder a data folder used as cache by the virtualenv
False start with empty app data folder
False trigger a manual update of the embedded wheels
verbosity ⇒ verbosity = verbose - quiet, default INFO, mapping => CRITICAL=0, ERROR=1, WARNING=2, INFO=3, DEBUG=4, NOTSET=5
2 increase verbosity
0 decrease verbosity

core ⇒ options shared across all discovery
builtin interpreter discovery method; choice of: builtin
the python executable virtualenv is installed into interpreter based on what to create environment (path/identifier) - by default use the interpreter where the tool is installed - first found wins
[] try first these interpreters before starting the discovery

core ⇒ options shared across all creator
builtin if exist, else venv create environment via; choice of: cpython2-mac-arm-framework, cpython2-mac-framework, cpython2-posix, cpython2-win, cpython3-mac-framework, cpython3-posix, cpython3-win, pypy2-posix, pypy2-win, pypy3-posix, pypy3-win, venv
directory to create virtualenv at
False remove the destination directory if exist before starting (will overwrite files otherwise)
False don't create VCS ignore directive in the destination directory
False give the virtual environment access to the system site-packages dir
True try to use symlinks rather than copies, when symlinks are not the default for the platform
False try to use copies rather than symlinks, even when symlinks are the default for the platform

core ⇒ options shared across all seeder
app-data seed packages install method; choice of: app-data, pip
False do not install seed packages
True pass to disable download of the latest pip/setuptools/wheel from PyPI
False pass to enable download of the latest pip/setuptools/wheel from PyPI
[] a path containing wheels to extend the internal wheel list (can be set 1+ times)
bundle version of pip to install as seed: embed, bundle or exact version
bundle version of setuptools to install as seed: embed, bundle or exact version
bundle version of wheel to install as seed: embed, bundle or exact version
False do not install pip
False do not install setuptools
False do not install wheel
False disable the periodic (once every 14 days) update of the embedded wheels
app-data ⇒ options specific to seeder app-data
False symlink the python packages from the app-data folder (requires seed pip>=19.3)

core ⇒ options shared across all activators
comma separated list of activators supported activators to generate - default is all supported; choice of: bash, batch, cshell, fish, nushell, powershell, python, xonsh
provides an alternative prompt prefix for this environment (value of . means name of the current working directory)

virtualenv looks for a standard ini configuration file. The exact location depends on the operating system you're using, as determined by platformdirs application configuration definition. The configuration file location is printed as at the end of the output when --help is passed.

The keys of the settings are derived from the command line option (left strip the - characters, and replace - with _). Where multiple flags are available first found wins (where order is as it shows up under the --help).

For example, --python would be specified as:

python = /opt/python-3.8/bin/python

Options that take multiple values, like extra-search-dir can be specified as:

extra_search_dir =


Default values may be also specified via environment variables. The keys of the settings are derived from the command line option (left strip the - characters, and replace - with _, finally capitalize the name). Where multiple flags are available first found wins (where order is as it shows up under the --help).

For example, to use a custom Python binary, instead of the one virtualenv is run with, you can set the environment variable VIRTUALENV_PYTHON like:

env VIRTUALENV_PYTHON=/opt/python-3.8/bin/python virtualenv

Where the option accepts multiple values, for example for python or extra-search-dir, the values can be separated either by literal newlines or commas. Newlines and commas can not be mixed and if both are present only the newline is used for separating values. Examples for multiple values:

env VIRTUALENV_PYTHON=/opt/python-3.8/bin/python,python3.8 virtualenv
env VIRTUALENV_EXTRA_SEARCH_DIR=/path/to/dists\n/path/to/other/dists virtualenv

The equivalent CLI-flags based invocation for the above examples would be:

virtualenv --python=/opt/python-3.8/bin/python --python=python3.8
virtualenv --extra-search-dir=/path/to/dists --extra-search-dir=/path/to/other/dists

virtualenv allows one to extend the builtin functionality via a plugin system. To add a plugin you need to:

  • write a python file containing the plugin code which follows our expected interface,
  • package it as a python library,
  • install it alongside the virtual environment.


The public API of some of these components is still to be finalized, consider the current interface a beta one until we get some feedback on how well we planned ahead. We expect to do this by end of Q3 2020. Consider the class interface explained below as initial draft proposal. We reserve the right to change the API until then, however such changes will be communicated in a timely fashion, and you'll have time to migrate. Thank you for your understanding.

Python discovery

The python discovery mechanism is a component that needs to answer the following answer: based on some type of user input give me a Python interpreter on the machine that matches that. The builtin interpreter tries to discover an installed Python interpreter (based on PEP-515 and PATH discovery) on the users machine where the user input is a python specification. An alternative such discovery mechanism for example would be to use the popular pyenv project to discover, and if not present install the requested Python interpreter. Python discovery mechanisms must be registered under key virtualenv.discovery, and the plugin must implement

virtualenv.discovery =

pyenv = virtualenv_pyenv.discovery:PyEnvDiscovery
Discover and provide the requested Python interpreter

Create a new discovery mechanism.

options -- the parsed options as defined within add_parser_arguments()
Add CLI arguments for this discovery mechanisms.
parser -- the CLI parser
Discovers an interpreter.
the interpreter ready to use for virtual environment creation
the interpreter as returned by run(), cached

Creators are what actually perform the creation of a virtual environment. The builtin virtual environment creators all achieve this by referencing a global install; but would be just as valid for a creator to install a brand new entire python under the target path; or one could add additional creators that can create virtual environments for other python implementations, such as IronPython. They must be registered under and entry point with key virtualenv.discovery , and the class must implement virtualenv.create.creator.Creator:

virtualenv.create =

cpython3-posix = virtualenv.create.via_global_ref.builtin.cpython.cpython3:CPython3Posix
A class that given a python Interpreter creates a virtual environment

Construct a new virtual environment creator.

  • options -- the CLI option as parsed from add_parser_arguments()
  • interpreter -- the interpreter to create virtual environment from
Determine if we can create a virtual environment.
interpreter -- the interpreter in question
None if we can't create, any other object otherwise that will be forwarded to add_parser_arguments()
Add CLI arguments for the creator.
  • parser -- the CLI parser
  • app_data -- the application data folder
  • interpreter -- the interpreter we're asked to create virtual environment for
  • meta -- value as returned by can_create()
Perform the virtual environment creation.
Generate ignore instructions for version control systems.

Seeders are what given a virtual environment will install somehow some seed packages into it. They must be registered under and entry point with key virtualenv.seed , and the class must implement virtualenv.seed.seeder.Seeder:

virtualenv.seed =

db = virtualenv.seed.fromDb:InstallFromDb
A seeder will install some seed packages into a virtual environment.
  • options -- the parsed options as defined within add_parser_arguments()
  • enabled -- a flag weather the seeder is enabled or not
Add CLI arguments for this seed mechanisms.
  • parser -- the CLI parser
  • app_data -- the CLI parser
  • interpreter -- the interpreter this virtual environment is based of
Perform the seed operation.
creator -- the creator (based of virtualenv.create.creator.Creator) we used to create this virtual environment

If you want add an activator for a new shell you can do this by implementing a new activator. They must be registered under and entry point with key virtualenv.activate , and the class must implement virtualenv.activation.activator.Activator:

virtualenv.activate =

bash = virtualenv.activation.bash:BashActivator
Generates an activate script for the virtual environment

Create a new activator generator.

options -- the parsed options as defined within add_parser_arguments()
Check if the activation script is supported in the given interpreter.
interpreter -- the interpreter we need to support
True if supported, False otherwise
Add CLI arguments for this activation script.
  • parser -- the CLI parser
  • interpreter -- the interpreter this virtual environment is based of
Generate the activate script for the given creator.
creator -- the creator (based of virtualenv.create.creator.Creator) we used to create this virtual environment

virtualenv is a volunteer maintained open source project and we welcome contributions of all forms. The sections below will help you get started with development, testing, and documentation. We’re pleased that you are interested in working on virtualenv. This document is meant to get you setup to work on virtualenv and to act as a guide and reference to the development setup. If you face any issues during this process, please open an issue about it on the issue tracker.

virtualenv is a command line application written in Python. To work on it, you'll need:

git clone
cd virtualenv
  • Python interpreter: We recommend using CPython. You can use this guide to set it up.
  • tox: to automatically get the projects development dependencies and run the test suite. We recommend installing it using pipx.

The easiest way to do this is to generate the development tox environment, and then invoke virtualenv from under the .tox/dev folder

tox -e dev
.tox/dev/bin/virtualenv  # on Linux
.tox/dev/Scripts/virtualenv  # on Windows

virtualenv's tests are written using the pytest test framework. tox is used to automate the setup and execution of virtualenv's tests.

To run tests locally execute:

tox -e py

This will run the test suite for the same Python version as under which tox is installed. Alternatively you can specify a specific version of python by using the pyNN format, such as: py38, pypy3, etc.

tox has been configured to forward any additional arguments it is given to pytest. This enables the use of pytest's rich CLI. As an example, you can select tests using the various ways that pytest provides:

# Using markers
tox -e py -- -m "not slow"
# Using keywords
tox -e py -- -k "test_extra"

Some tests require additional dependencies to be run, such is the various shell activators (bash, fish, powershell, etc). These tests will automatically be skipped if these are not present, note however that in CI all tests are run; so even if all tests succeed locally for you, they may still fail in the CI.

virtualenv uses pre-commit for managing linting of the codebase. pre-commit performs various checks on all files in virtualenv and uses tools that help follow a consistent code style within the codebase. To use linters locally, run:

tox -e fix_lint


Avoid using # noqa comments to suppress linter warnings - wherever possible, warnings should be fixed instead. # noqa comments are reserved for rare cases where the recommended style causes severe readability problems.

virtualenv's documentation is built using Sphinx. The documentation is written in reStructuredText. To build it locally, run:

tox -e docs

The built documentation can be found in the .tox/docs_out folder and may be viewed by opening index.html within that folder.

virtualenv's release schedule is tied to pip, setuptools and wheel. We bundle the latest version of these libraries so each time there's a new version of any of these, there will be a new virtualenv release shortly afterwards (we usually wait just a few days to avoid pulling in any broken releases).

Submit pull requests against the main branch, providing a good description of what you're doing and why. You must have legal permission to distribute any code you contribute to virtualenv and it must be available under the MIT License. Provide tests that cover your changes and run the tests locally first. virtualenv supports multiple Python versions and operating systems. Any pull request must consider and work on all these platforms.

Pull Requests should be small to facilitate review. Keep them self-contained, and limited in scope. Studies have shown that review quality falls off as patch size grows. Sometimes this will result in many small PRs to land a single large feature. In particular, pull requests must not be treated as "feature branches", with ongoing development work happening within the PR. Instead, the feature should be broken up into smaller, independent parts which can be reviewed and merged individually.

Additionally, avoid including "cosmetic" changes to code that is unrelated to your change, as these make reviewing the PR more difficult. Examples include re-flowing text in comments or documentation, or addition or removal of blank lines or whitespace within lines. Such changes can be made separately, as a "formatting cleanup" PR, if needed.

All pull requests and merges to 'main' branch are tested using Azure Pipelines (configured by azure-pipelines.yml file at the root of the repository). You can find the status and results to the CI runs for your PR on GitHub's Web UI for the pull request. You can also find links to the CI services' pages for the specific builds in the form of "Details" links, in case the CI run fails and you wish to view the output.

To trigger CI to run again for a pull request, you can close and open the pull request or submit another change to the pull request. If needed, project maintainers can manually trigger a restart of a job/build.

The changelog.rst file is managed using towncrier and all non trivial changes must be accompanied by a news entry. To add an entry to the news file, first you need to have created an issue describing the change you want to make. A Pull Request itself may function as such, but it is preferred to have a dedicated issue (for example, in case the PR ends up rejected due to code quality reasons).

Once you have an issue or pull request, you take the number and you create a file inside of the docs/changelog directory named after that issue number with an extension of:

  • feature.rst,
  • bugfix.rst,
  • doc.rst,
  • removal.rst,
  • misc.rst.

Thus if your issue or PR number is 1234 and this change is fixing a bug, then you would create a file docs/changelog/1234.bugfix.rst. PRs can span multiple categories by creating multiple files (for instance, if you added a feature and deprecated/removed the old feature at the same time, you would create docs/changelog/1234.bugfix.rst and docs/changelog/1234.remove.rst). Likewise if a PR touches multiple issues/PRs you may create a file for each of them with the same contents and towncrier will deduplicate them.

The contents of this file are reStructuredText formatted text that will be used as the content of the news file entry. You do not need to reference the issue or PR numbers here as towncrier will automatically add a reference to all of the affected issues when rendering the news file.

In order to maintain a consistent style in the changelog.rst file, it is preferred to keep the news entry to the point, in sentence case, shorter than 120 characters and in an imperative tone -- an entry should complete the sentence This change will …. In rare cases, where one line is not enough, use a summary line in an imperative tone followed by a blank line separating it from a description of the feature/change in one or more paragraphs, each wrapped at 120 characters. Remember that a news entry is meant for end users and should only contain details relevant to an end user.

A trivial change is anything that does not warrant an entry in the news file. Some examples are: code refactors that don't change anything as far as the public is concerned, typo fixes, white space modification, etc. To mark a PR as trivial a contributor simply needs to add a randomly named, empty file to the news/ directory with the extension of .trivial.

If you want to become an official maintainer, start by helping out. As a first step, we welcome you to triage issues on virtualenv's issue tracker. virtualenv maintainers provide triage abilities to contributors once they have been around for some time and contributed positively to the project. This is optional and highly recommended for becoming a virtualenv maintainer. Later, when you think you're ready, get in touch with one of the maintainers and they will initiate a vote among the existing maintainers.


Upon becoming a maintainer, a person should be given access to various virtualenv-related tooling across multiple platforms. These are noted here for future reference by the maintainers:
  • GitHub Push Access
  • PyPI Publishing Access
  • CI Administration capabilities
  • ReadTheDocs Administration capabilities

python -m towncrier, version 22.8.0

Bugfixes - 20.15.1

  • Fix the incorrect operation when setuptools plugins output something into stdout. (#2335)
  • CPython3Windows creator ignores missing DLLs dir. (#2368)

Features - 20.15.0

Support for Windows embeddable Python package: includes python<VERSION>.zip in the creator sources - by @reksarka. (#1774)

Bugfixes - 20.15.0

  • Upgrade embedded setuptools to 62.3.3 from 62.6.0 and pip to 22.1.2 from 22.0.4 - by @gaborbernat. (#2348)
  • Use shlex.quote instead of deprecated pipes.quote in Python 3 - by @frenzymadness. (#2351)
  • Fix Windows PyPy 3.6 - by @reksarka. (#2363)

Features - 20.14.1

Support for creating a virtual environment from a Python 2.7 framework on macOS 12 - by @nickhutchinson. (#2284)

Bugfixes - 20.14.1

Upgrade embedded setuptools to 62.1.0 from 61.0.0 - by @gaborbernat. (#2327)

Features - 20.14.0

Support Nushell activation scripts with nu version 0.60 - by @kubouch. (#2321)

Bugfixes - 20.14.0

Upgrade embedded setuptools to 61.0.0 from 60.10.0 - by @gaborbernat. (#2322)

Bugfixes - 20.14.0

  • Improve performance of python startup inside created virtualenvs - by @asottile. (#2317)
  • Upgrade embedded setuptools to 60.10.0 from 60.9.3 - by @gaborbernat. (#2320)

Bugfixes - 20.13.3

  • Avoid symlinking the contents of /usr into PyPy3.8+ virtualenvs - by @stefanor. (#2310)
  • Bump embed pip from 22.0.3 to 22.0.4 - by @gaborbernat. (#2311)

Bugfixes - 20.13.2

Upgrade embedded setuptools to 60.9.3 from 60.6.0 - by @gaborbernat. (#2306)

Bugfixes - 20.13.1

  • fix "execv() arg 2 must contain only strings" error on M1 MacOS (#2282)
  • Ugrade embedded setuptools to 60.5.0 from 60.2.0 - by @asottile. (#2289)
  • Upgrade embedded pip to 22.0.3 and setuptools to 60.6.0 - by @gaborbernat and @asottile. (#2294)

Features - 20.13.0

Add downloaded wheel information in the relevant JSON embed file to prevent additional downloads of the same wheel. - by @mayeut. (#2268)

Bugfixes - 20.13.0

  • Fix AttributeError: 'bool' object has no attribute 'error' when creating a Python 2.x virtualenv on macOS - by moreati. (#2269)
  • Fix PermissionError: [Errno 1] Operation not permitted when creating a Python 2.x virtualenv on macOS/arm64 - by moreati. (#2271)

Bugfixes - 20.12.1

  • Try using previous updates of pip, setuptools & wheel when inside an update grace period rather than always falling back to embedded wheels - by @mayeut. (#2265)
  • New patch versions of pip, setuptools & wheel are now returned in the expected timeframe. - by @mayeut. (#2266)
  • Manual upgrades of pip, setuptools & wheel are not discarded by a periodic update - by @mayeut. (#2267)

Features - 20.12.0

Sign the python2 exe on Darwin arm64 - by @tmspicer. (#2233)

Bugfixes - 20.12.0

  • Fix --download option - by @mayeut. (#2120)
  • Ugrade embedded setuptools to 60.2.0 from 60.1.1 - by @gaborbernat. (#2263)

Bugfixes - 20.11.2

Fix installation of pinned versions of pip, setuptools & wheel - by @mayeut. (#2203)

Bugfixes - 20.11.1

Bump embed setuptools to 60.1.1 from 60.1.0 - by @gaborbernat. (#2258)

Features - 20.11.0

  • Avoid deprecation warning from py-filelock argument - by @ofek. (#2237)
  • Upgrade embedded setuptools to 61.1.0 from 58.3.0 - by @gaborbernat. (#2240)
  • Drop the runtime dependency of backports.entry-points-selectable - by @hroncok. (#2246)
  • Fish: PATH variables should not be quoted when being set - by @hroncok. (#2248)

Features - 20.10.0

  • If a "venv" install scheme exists in sysconfig, virtualenv now uses it to create new virtual environments. This allows Python distributors, such as Fedora, to patch/replace the default install scheme without affecting the paths in new virtual environments. A similar technique was proposed to Python, for the venv module - by hroncok (#2208)
  • The activated virtualenv prompt is now always wrapped in parentheses. This affects venvs created with the --prompt attribute, and matches virtualenv's behaviour on par with venv. (#2224)

Bugfixes - 20.10.0

Fix broken prompt set up by activate.bat - by @SiggyBar. (#2225)

Features - 20.9.0

  • Special-case --prompt . to the name of the current directory - by @rkm. (#2220)
  • Add libffi-8.dll to pypy windows #2218 - by @mattip

Bugfixes - 20.9.0

  • Fixed path collision that could lead to a PermissionError or writing to system directories when using PyPy3.8 - by @mgorny. (#2182)
  • Upgrade embedded setuptools to 58.3.0 from 58.1.0 and pip to 21.3.1 from 21.2.4 - by @gaborbernat. (#2205)
  • Remove stray closing parenthesis in activate.bat - by @SiggyBar. (#2221)

Bugfixes - 20.8.1

  • Fixed a bug where while creating a venv on top of an existing one, without cleaning, when seeded wheel version mismatch occurred, multiple .dist-info directories may be present, confounding entrypoint discovery - by @arcivanov (#2185)
  • Bump embed setuptools from 58.0.4 to 58.1.0 - by @gaborbernat. (#2195)


  • upgrade embedded setuptools to 58.0.4 from 57.4.0 and pip to 21.2.4 from 21.2.3
  • Add nushell activation script

Bugfixes - 20.7.2

Upgrade embedded pip to 21.2.3 from 21.2.2 and wheel to 0.37.0 from 0.36.2 - by @gaborbernat. (#2168)

Bugfixes - 20.7.1

Fix unpacking dictionary items in PythonInfo.install_path (#2165)

Bugfixes - 20.7.0

upgrade embedded pip to 21.2.2 from 21.1.3 and setuptools to 57.4.0 from 57.1.0 - by @gaborbernat (#2159)

Deprecations and Removals - 20.7.0

Removed xonsh activator due to this breaking fairly often the CI and lack of support from those packages maintainers, upstream is encouraged to continue supporting the project as a plugin - by @gaborbernat. (#2160)

Features - 20.6.0

Support Python interpreters without distutils (fallback to syconfig in these cases) - by @gaborbernat. (#1910)

Features - 20.5.0

  • Plugins now use 'selectable' entry points - by @jaraco. (#2093)
  • add libffi-7.dll to the hard-coded list of dlls for PyPy (#2141)
  • Use the better maintained platformdirs instead of appdirs - by @gaborbernat. (#2142)

Bugfixes - 20.5.0

Bump pip the embedded pip 21.1.3 and setuptools to 57.1.0 - by @gaborbernat. (#2135)

Deprecations and Removals - 20.5.0

Drop python 3.4 support as it has been over 2 years since EOL - by @gaborbernat. (#2141)

Bugfixes - 20.4.7

Upgrade embedded pip to 21.1.2 and setuptools to 57.0.0 - by @gaborbernat. (#2123)

Bugfixes - 20.4.6

Fix site.getsitepackages() broken on python2 on debian - by @freundTech. (#2105)

Bugfixes - 20.4.5

  • Bump pip to 21.1.1 from 21.0.1 - by @gaborbernat. (#2104)
  • Fix site.getsitepackages() ignoring --system-site-packages on python2 - by @freundTech. (#2106)

Bugfixes - 20.4.4

  • Built in discovery class is always preferred over plugin supplied classes. (#2087)
  • Upgrade embedded setuptools to 56.0.0 by @gaborbernat. (#2094)

Bugfixes - 20.4.3

  • Bump embedded setuptools from 52.0.0 to 54.1.2 - by @gaborbernat (#2069)
  • Fix PyPy3 stdlib on Windows is incorrect - by @gaborbernat. (#2071)

Bugfixes - 20.4.2

Running virtualenv --upgrade-embed-wheels crashes - by @gaborbernat. (#2058)

Bugfixes - 20.4.1

Bump embedded pip and setuptools packages to latest upstream supported (21.0.1 and 52.0.0) - by @gaborbernat. (#2060)

Features - 20.4.0

On the programmatic API allow passing in the environment variable dictionary to use, defaults to os.environ if not specified - by @gaborbernat. (#2054)

Bugfixes - 20.4.0

Upgrade embedded setuptools to 51.3.3 from 51.1.2 - by @gaborbernat. (#2055)

Bugfixes - 20.3.1

  • Bump embed pip to 20.3.3, setuptools to 51.1.1 and wheel to 0.36.2 - by @gaborbernat. (#2036)
  • Allow unfunctioning of pydoc to fail freely so that virtualenvs can be activated under Zsh with set -e (since otherwise unset -f and unfunction exit with 1 if the function does not exist in Zsh) - by @d125q. (#2049)
  • Drop cached python information if the system executable is no longer present (for example when the executable is a shim and the mapped executable is replaced - such is the case with pyenv) - by @gaborbernat. (#2050)

Features - 20.3.0

The builtin discovery takes now a --try-first-with argument and is first attempted as valid interpreters. One can use this to force discovery of a given python executable when the discovery order/mechanism raises errors - by @gaborbernat. (#2046)

Bugfixes - 20.3.0

  • On Windows python 3.7+ distributions where the exe shim is missing fallback to the old ways - by @gaborbernat. (#1986)
  • When discovering interpreters on Windows, via the PEP-514, prefer PythonCore releases over other ones. virtualenv is used via pip mostly by this distribution, so prefer it over other such as conda - by @gaborbernat. (#2046)

Bugfixes - 20.2.2

Bump pip to 20.3.1, setuptools to 51.0.0 and wheel to 0.36.1 - by @gaborbernat. (#2029)

No significant changes.

Features - 20.2.0

  • Optionally skip VCS ignore directive for entire virtualenv directory, using option no-vcs-ignore, by default False. (#2003)
  • Add --read-only-app-data option to allow for creation based on an existing app data cache which is non-writable. This may be useful (for example) to produce a docker image where the app-data is pre-populated.

VIRTUALENV_OVERRIDE_APP_DATA=/opt/virtualenv/cache \
VIRTUALENV_SYMLINK_APP_DATA=1 RUN virtualenv venv && rm -rf venv ENV VIRTUALENV_READ_ONLY_APP_DATA=1 USER nobody # this virtualenv has symlinks into the read-only app-data cache RUN virtualenv /tmp/venv

Patch by @asottile. (#2009)

Bugfixes - 20.2.0

Fix processing of the VIRTUALENV_PYTHON environment variable and make it multi-value as well (separated by comma) - by @pneff. (#1998)

Features - 20.1.0

The python specification can now take one or more values, first found is used to create the virtual environment - by @gaborbernat. (#1995)

Bugfixes - 20.0.35

  • Bump embedded setuptools from 50.3.0 to 50.3.1 - by @gaborbernat. (#1982)
  • After importing virtualenv passing cwd to a subprocess calls breaks with invalid directory - by @gaborbernat. (#1983)

Bugfixes - 20.0.34

  • Align with venv module when creating virtual environments with builtin creator on Windows 3.7 and later - by @gaborbernat. (#1782)
  • Handle Cygwin path conversion in the activation script - by @davidcoghlan. (#1969)

Bugfixes - 20.0.33

  • Fix None type error in cygwin if POSIX path in dest - by @danyeaw. (#1962)
  • Fix Python 3.4 incompatibilities (added back to the CI) - by @gaborbernat. (#1963)

Bugfixes - 20.0.32

  • For activation scripts always use UNIX line endings (unless it's BATCH shell related) - by @saytosid. (#1818)
  • Upgrade embedded pip to 20.2.1 and setuptools to 49.4.0 - by @gaborbernat. (#1918)
  • Avoid spawning new windows when doing seed package upgrades in the background on Windows - by @gaborbernat. (#1928)
  • Fix a bug that reading and writing on the same file may cause race on multiple processes. (#1938)
  • Upgrade embedded setuptools to 50.2.0 and pip to 20.2.3 - by @gaborbernat. (#1939)
  • Provide correct path for bash activator in cygwin or msys2 - by @danyeaw. (#1940)
  • Relax importlib requirement to allow version<3 - by @usamasadiq (#1953)
  • pth files were not processed on CPython2 if $PYTHONPATH was pointing to site-packages/ - by @navytux. (#1959) (#1960)

Bugfixes - 20.0.31

Upgrade embedded pip to 20.2.1, setuptools to 49.6.0 and wheel to 0.35.1 - by @gaborbernat. (#1918)

Bugfixes - 20.0.30

Upgrade pip to 20.2.1 and setuptools to 49.2.1 - by @gaborbernat. (#1915)

Bugfixes - 20.0.29

Upgrade embedded pip from version 20.1.2 to 20.2 - by @gaborbernat. (#1909)

Bugfixes - 20.0.28

  • Fix test suite failing if run from system Python - by @gaborbernat. (#1882)
  • Provide setup_logging flag to python API so that users can bypass logging handling if their application already performs this - by @gaborbernat. (#1896)
  • Use \n instead if \r\n as line separator for report (because Python already performs this transformation automatically upon write to the logging pipe) - by @gaborbernat. (#1905)

Bugfixes - 20.0.27

  • No longer preimport threading to fix support for gpython and gevent - by @navytux. (#1897)
  • Upgrade setuptools from 49.2.0 on Python 3.5+ - by @gaborbernat. (#1898)

Bugfixes - 20.0.26

  • Bump dependency distutils >= 0.3.1 - by @gaborbernat. (#1880)
  • Improve periodic update handling:
  • better logging output while running and enable logging on background process call ( _VIRTUALENV_PERIODIC_UPDATE_INLINE may be used to debug behaviour inline)
  • fallback to unverified context when querying the PyPi for release date,
  • stop downloading wheels once we reach the embedded version,

by @gaborbernat. (#1883)

  • Do not print error message if the application exists with SystemExit(0) - by @gaborbernat. (#1885)
  • Upgrade embedded setuptools from 47.3.1 to 49.1.0 for Python 3.5+ - by @gaborbernat. (#1887)

Bugfixes - 20.0.25

Fix that when the app-data seeders image creation fails the exception is silently ignored. Avoid two virtual environment creations to step on each others toes by using a lock while creating the base images. By @gaborbernat. (#1869)

Features - 20.0.24

Ensure that the seeded packages do not get too much out of date:
  • add a CLI flag that triggers upgrade of embedded wheels under upgrade-embed-wheels
  • periodically (once every 14 days) upgrade the embedded wheels in a background process, and use them if they have been released for more than 28 days (can be disabled via no-periodic-update)

More details under Wheels - by @gaborbernat. (#1821)

Upgrade embed wheel content:
  • ship wheels for Python 3.9 and 3.10
  • upgrade setuptools for Python 3.5+ from 47.1.1 to 47.3.1

by @gaborbernat. (#1841)

Display the installed seed package versions in the final summary output, for example:
created virtual environment in 350ms

creator CPython3Posix(dest=/x, clear=True, global=False)
seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/y/virtualenv)
added seed packages: pip==20.1.1, setuptools==47.3.1, wheel==0.34.2

by @gaborbernat. (#1864)

Bugfixes - 20.0.24

  • Do not generate/overwrite .gitignore if it already exists at destination path - by @gaborbernat. (#1862)
  • Improve error message for no .dist-info inside the app-data copy seeder - by @gaborbernat. (#1867)

Improved Documentation - 20.0.24

  • How seeding mechanisms discover (and automatically keep it up to date) wheels at Wheels - by @gaborbernat. (#1821)
  • How distributions should handle shipping their own embedded wheels at Embed wheels for distributions - by @gaborbernat. (#1840)

Bugfixes - 20.0.23

Fix typo in setup.cfg - by @RowdyHowell. (#1857)

Bugfixes - 20.0.22

  • Relax importlib.resources requirement to also allow version 2 - by @asottile. (#1846)
  • Upgrade embedded setuptools to 44.1.1 for python 2 and 47.1.1 for python3.5+ - by @gaborbernat. (#1855)

Features - 20.0.21

Generate ignore file for version control systems to avoid tracking virtual environments by default. Users should remove these files if still want to track. For now we support only git by @gaborbernat. (#1806)

Bugfixes - 20.0.21

  • Fix virtualenv fails sometimes when run concurrently, --clear-app-data conflicts with clear flag when abbreviation is turned on. To bypass this while allowing abbreviated flags on the command line we had to move it to reset-app-data - by @gaborbernat. (#1824)
  • Upgrade embedded setuptools to 46.4.0 from 46.1.3 on Python 3.5+, and pip from 20.1 to 20.1.1 - by @gaborbernat. (#1827)
  • Seeder pip now correctly handles --extra-search-dir - by @frenzymadness. (#1834)

Bugfixes - 20.0.20

  • Fix download fails with python 3.4 - by @gaborbernat. (#1809)
  • Fixes older CPython2 versions use _get_makefile_filename instead of get_makefile_filename on sysconfig - by @ianw. (#1810)
  • Fix download is True by default - by @gaborbernat. (#1813)
  • Fail app-data seed operation when wheel download fails and better error message - by @gaborbernat. (#1814)

Bugfixes - 20.0.19

  • Fix generating a Python 2 environment from Python 3 creates invalid python activator - by @gaborbernat. (#1776)
  • Fix pinning seed packages via app-data seeder raised Invalid Requirement - by @gaborbernat. (#1779)
  • Do not stop interpreter discovery if we fail to find the system interpreter for a executable during discovery - by @gaborbernat. (#1781)
  • On CPython2 POSIX platforms ensure syconfig.get_makefile_filename exists within the virtual environment (this is used by some c-extension based libraries - e.g. numpy - for building) - by @gaborbernat. (#1783)
  • Better handling of options copies and symlinks. Introduce priority of where the option is set to follow the order: CLI, env var, file, hardcoded. If both set at same level prefers copy over symlink. - by @gaborbernat. (#1784)
  • Upgrade pip for Python 2.7 and 3.5+ from 20.0.2 to 20.1 - by @gaborbernat. (#1793)
  • Fix CPython is not discovered from Windows registry, and discover pythons from Windows registry in decreasing order by version - by @gaborbernat. (#1796)
  • Fix symlink detection for creators - by @asottile (#1803)

Bugfixes - 20.0.18

Importing setuptools before cli_run could cause our python information query to fail due to setuptools patching distutils.dist.Distribution - by @gaborbernat. (#1771)

Features - 20.0.17

Extend environment variables checked for configuration to also check aliases (e.g. setting either VIRTUALENV_COPIES or VIRTUALENV_ALWAYS_COPY will work) - by @gaborbernat. (#1763)

Bugfixes - 20.0.16

Allow seed wheel files inside the extra-search-dir folders that do not have Requires-Python metadata specified, these are considered compatible with all python versions - by @gaborbernat. (#1757)

Features - 20.0.15

Upgrade embedded setuptools to 46.1.3 from 46.1.1 - by @gaborbernat. (#1752)

Features - 20.0.14

  • Remove __PYVENV_LAUNCHER__ on macOs for Python 3.7.(<8) and 3.8.(<3) on interpreter startup via pth file, this pulls in the upstream patch - by @gaborbernat. (#1704)
  • Upgrade embedded setuptools for Python 3.5+ to 46.1.1, for Python 2.7 to 44.1.0 - by @gaborbernat. (#1745)

Bugfixes - 20.0.14

Fix discovery of interpreter by name from PATH that does not match a spec format - by @gaborbernat. (#1746)

Bugfixes - 20.0.13

  • Do not fail when the pyc files is missing for the host Python 2 - by @gaborbernat. (#1738)
  • Support broken Packaging pythons that put the include headers under distutils pattern rather than sysconfig one - by @gaborbernat. (#1739)

Bugfixes - 20.0.12

Fix relative path discovery of interpreters - by @gaborbernat. (#1734)

Features - 20.0.11

Improve error message when the host python does not satisfy invariants needed to create virtual environments (now we print which host files are incompatible/missing and for which creators when no supported creator can be matched, however we found creators that can describe the given Python interpreter - will still print no supported creator for Jython, however print exactly what host files do not allow creation of virtual environments in case of CPython/PyPy) - by @gaborbernat. (#1716)

Bugfixes - 20.0.11

  • Support Python 3 Framework distributed via XCode in macOs Catalina and before - by @gaborbernat. (#1663)
  • Fix Windows Store Python support, do not allow creation via symlink as that's not going to work by design - by @gaborbernat. (#1709)
  • Fix throws AttributeError on Windows when virtual environment was created via cross python mechanism - by @gaborbernat. (#1710)
  • Fix --no-pip, --no-setuptools, --no-wheel not being respected - by @gaborbernat. (#1712)
  • Allow missing .py files if a compiled .pyc version is available - by @tucked. (#1714)
  • Do not fail if the distutils/setuptools patch happens on a C-extension loader (such as zipimporter on Python 3.7 or earlier) - by @gaborbernat. (#1715)
  • Support Python 2 implementations that require the landmark files and to be in platform standard library instead of the standard library path of the virtual environment (notably some RHEL ones, such as the Docker image amazonlinux:1) - by @gaborbernat. (#1719)
  • Allow the test suite to pass even when called with the system Python - to help repackaging of the tool for Linux distributions - by @gaborbernat. (#1721)
  • Also generate pipx.y console script beside pip-x.y to be compatible with how pip installs itself - by @gaborbernat. (#1723)
  • Automatically create the application data folder if it does not exists - by @gaborbernat. (#1728)

Improved Documentation - 20.0.11

supports details now explicitly what Python installations we support - by @gaborbernat. (#1714)

Bugfixes - 20.0.10

  • Fix acquiring python information might be altered by distutils configuration files generating incorrect layout virtual environments - by @gaborbernat. (#1663)
  • Upgrade embedded setuptools to 46.0.0 from 45.3.0 on Python 3.5+ - by @gaborbernat. (#1702)

Improved Documentation - 20.0.10

  • Document requirements (pip + index server) when installing via pip under the installation section - by @gaborbernat. (#1618)
  • Document installing from non PEP-518 systems - @gaborbernat. (#1619)
  • Document installing latest unreleased version from Github - @gaborbernat. (#1620)

Bugfixes - 20.0.9

  • pythonw.exe works as python.exe on Windows - by @gaborbernat. (#1686)
  • Handle legacy loaders for virtualenv import hooks used to patch distutils configuration load - by @gaborbernat. (#1690)
  • Support for python 2 platforms that store landmark files in platstdlib over stdlib (e.g. RHEL) - by @gaborbernat. (#1694)
  • Upgrade embedded setuptools to 45.3.0 from 45.2.0 for Python 3.5+ - by @gaborbernat. (#1699)

Bugfixes - 20.0.8

  • Having distutils configuration files that set prefix and install_scripts cause installation of packages in the wrong location - by @gaborbernat. (#1663)
  • Fix PYTHONPATH being overridden on Python 2 — by @jd. (#1673)
  • Fix list configuration value parsing from config file or environment variable - by @gaborbernat. (#1674)
  • Fix Batch activation script shell prompt to display environment name by default - by @spetafree. (#1679)
  • Fix startup on Python 2 is slower for virtualenv - this was due to setuptools calculating it's working set distribution - by @gaborbernat. (#1682)
  • Fix entry points are not populated for editable installs on Python 2 due to setuptools working set being calculated before easy_install.pth runs - by @gaborbernat. (#1684)
  • Fix attr: import fails for setuptools - by @gaborbernat. (#1685)

Bugfixes - 20.0.7

Disable distutils fixup for python 3 until pypa/pip #7778 is fixed and released - by @gaborbernat. (#1669)

Bugfixes - 20.0.6

  • Fix global site package always being added with bundled macOs python framework builds - by @gaborbernat. (#1561)
  • Fix generated scripts use host version info rather than target - by @gaborbernat. (#1600)
  • Fix circular prefix reference with single elements (accept these as if they were system executables, print a info about them referencing themselves) - by @gaborbernat. (#1632)
  • Handle the case when the application data folder is read-only:
  • the application data folder is now controllable via app-data,
  • clear-app-data now cleans the entire application data folder, not just the app-data seeder path,
  • check if the application data path passed in does not exist or is read-only, and fallback to a temporary directory,
  • temporary directory application data is automatically cleaned up at the end of execution,
  • symlink-app-data is always False when the application data is temporary

by @gaborbernat. (#1640)

  • Fix PyPy 2 builtin modules are imported from standard library, rather than from builtin - by @gaborbernat. (#1652)
  • Fix creation of entry points when path contains spaces - by @nsoranzo. (#1660)
  • Fix relative paths for the zipapp (for python 3.7+) - by @gaborbernat. (#1666)

Features - 20.0.5

  • Also create pythonX.X executables when creating pypy virtualenvs - by @asottile (#1612)
  • Fail with better error message if trying to install source with unsupported setuptools, allow setuptools-scm >= 2 and move to legacy setuptools-scm format to support better older platforms (CentOS 7 and such) - by @gaborbernat. (#1621)
  • Report of the created virtual environment is now split across four short lines rather than one long - by @gaborbernat (#1641)

Bugfixes - 20.0.5

  • Add macOs Python 2 Framework support (now we test it with the CI via brew) - by @gaborbernat (#1561)
  • Fix losing of when the pypy executable is a symlink - by @asottile (#1614)
  • Discover python interpreter in a case insensitive manner - by @PrajwalM2212 (#1624)
  • Fix cross interpreter support when the host python sets sys.base_executable based on __PYVENV_LAUNCHER__ - by @cjolowicz (#1643)

Features - 20.0.4

When aliasing interpreters, use relative symlinks - by @asottile. (#1596)

Bugfixes - 20.0.4

  • Allow the use of / as pathname component separator on Windows - by vphilippon (#1582)
  • Lower minimal version of six required to 1.9 - by ssbarnea (#1606)

Bugfixes - 20.0.3

  • On Python 2 with Apple Framework builds the global site package is no longer added when the system-site-packages is not specified - by @gaborbernat. (#1561)
  • Fix system python discovery mechanism when prefixes contain relative parts (e.g. ..) by resolving paths within the python information query - by @gaborbernat. (#1583)
  • Expose a programmatic API as from virtualenv import cli_run - by @gaborbernat. (#1585)
  • Fix app-data seeder injects a extra .dist-info.virtualenv path that breaks importlib.metadata, now we inject an extra .virtualenv - by @gaborbernat. (#1589)

Improved Documentation - 20.0.3

Document a programmatic API as from virtualenv import cli_run under Programmatic API - by @gaborbernat. (#1585)

Features - 20.0.2

  • Print out a one line message about the created virtual environment when no verbose is set, this can now be silenced to get back the original behaviour via the quiet flag - by @pradyunsg. (#1557)
  • Allow virtualenv's app data cache to be overridden by VIRTUALENV_OVERRIDE_APP_DATA - by @asottile. (#1559)
  • Passing in the virtual environment name/path is now required (no longer defaults to venv) - by @gaborbernat. (#1568)
  • Add a CLI flag with-traceback that allows displaying the stacktrace of the virtualenv when a failure occurs - by @gaborbernat. (#1572)

Bugfixes - 20.0.2

  • Support long path names for generated virtual environment console entry points (such as pip) when using the app-data seeder - by @gaborbernat. (#997)
  • Improve python discovery mechanism:
  • do not fail if there are executables that fail to query (e.g. for not having execute access to it) on the PATH,
  • beside the prefix folder also try with the platform dependent binary folder within that,

by @gaborbernat. (#1545)

  • When copying (either files or trees) do not copy the permission bits, last access time, last modification time, and flags as access to these might be forbidden (for example in case of the macOs Framework Python) and these are not needed for the user to use the virtual environment - by @gaborbernat. (#1561)
  • While discovering a python executables interpreters that cannot be queried are now displayed with info level rather than warning, so now they're no longer shown by default (these can be just executables to which we don't have access or that are broken, don't warn if it's not the target Python we want) - by @gaborbernat. (#1574)
  • The app-data seeder no longer symlinks the packages on UNIX and copies on Windows. Instead by default always copies, however now has the symlink-app-data flag allowing users to request this less robust but faster method - by @gaborbernat. (#1575)

Improved Documentation - 20.0.2

  • Add link to the legacy documentation for the changelog by @jezdez. (#1547)
  • Fine tune the documentation layout: default width of theme, allow tables to wrap around, soft corners for code snippets - by @pradyunsg. (#1548)

Features - 20.0.1

upgrade embedded setuptools to 45.2.0 from 45.1.0 for Python 3.4+ - by @gaborbernat. (#1554)

Bugfixes - 20.0.1

  • Virtual environments created via relative path on Windows creates bad console executables - by @gaborbernat. (#1552)
  • Seems sometimes venvs created set their base executable to themselves; we accept these without question, so we handle virtual environments as system pythons causing issues - by @gaborbernat. (#1553)

Improved Documentation - 20.0.0.

Fixes typos, repeated words and inconsistent heading spacing. Rephrase parts of the development documentation and CLI documentation. Expands shorthands like env var and config to their full forms. Uses descriptions from respective documentation, for projects listed in related links - by @pradyunsg. (#1540)

Features - 20.0.0b2

Improve base executable discovery mechanism:
  • print at debug level why we refuse some candidates,
  • when no candidates match exactly, instead of hard failing fallback to the closest match where the priority of matching attributes is: python implementation, major version, minor version, architecture, patch version, release level and serial (this is to facilitate things to still work when the OS upgrade replace/upgrades the system python with a never version, than what the virtualenv host python was created with),
  • always resolve system_executable information during the interpreter discovery, and the discovered environment is the system interpreter instead of the venv/virtualenv (this happened before lazily the first time we accessed, and caused reporting that the created virtual environment is of type of the virtualenv host python version, instead of the system pythons version - these two can differ if the OS upgraded the system python underneath and the virtualenv host was created via copy),

by @gaborbernat. (#1515)

  • Generate bash and fish activators on Windows too (as these can be available with git bash, cygwin or mysys2) - by @gaborbernat. (#1527)
  • Upgrade the bundled wheel package from 0.34.0 to 0.34.2 - by @gaborbernat. (#1531)

Bugfixes - 20.0.0b2

  • Bash activation script should have no extensions instead of .sh (this fixes the virtualenvwrapper integration) - by @gaborbernat. (#1508)
  • Show less information when we run with a single verbosity (-v):
  • no longer shows accepted interpreters information (as the last proposed one is always the accepted one),
  • do not display the str_spec attribute for PythonSpec as these can be deduced from the other attributes,
  • for the app-data seeder do not show the type of lock, only the path to the app data directory,

By @gaborbernat. (#1510)

  • Fixed cannot discover a python interpreter that has already been discovered under a different path (such is the case when we have multiple symlinks to the same interpreter) - by @gaborbernat. (#1512)
  • Support relative paths for -p - by @gaborbernat. (#1514)
  • Creating virtual environments in parallel fail with cannot acquire lock within app data - by @gaborbernat. (#1516)
  • pth files were not processed under Debian CPython2 interpreters - by @gaborbernat. (#1517)
  • Fix prompt not displayed correctly with upcoming fish 3.10 due to us not preserving $pipestatus - by @krobelus. (#1530)
  • Stable order within pyenv.cfg and add include-system-site-packages only for creators that reference a global Python - by user:gaborbernat. (#1535)

Improved Documentation - 20.0.0b2

  • Create the first iteration of the new documentation - by @gaborbernat. (#1465)
  • Project readme is now of type MarkDown instead of reStructuredText - by @gaborbernat. (#1531)

  • First public release of the rewrite. Everything is brand new and just added.
  • --download defaults to False


The current virtualenv is the second iteration of implementation. From version 0.8 all the way to 16.7.9 we numbered the first iteration. Version 20.0.0b1 is a complete rewrite of the package, and as such this release history starts from there. The old changelog is still available in the legacy branch documentation.


2007-2022, PyPA, PyPA

September 30, 2022 20.15