Virtualenv has one basic command:
$ virtualenv ENV
ENV is a directory to place the new virtual environment. It has
a number of usual effects (modifiable by many Options):
ENV/include/are created, containing supporting library files for a new virtualenv python. Packages installed in this environment will live under
ENV/binis created, where executables live - noticeably a new python. Thus running a script with
#! /path/to/ENV/bin/pythonwould run that script under this virtualenv’s python.
- The crucial packages pip and setuptools are installed, which allow other packages to be easily installed to the environment. This associated pip can be run from
The python in your new virtualenv is effectively isolated from the python that was used to create it.
In a newly created virtualenv there will also be a activate shell script. For Windows systems, activation scripts are provided for the Command Prompt and Powershell.
On Posix systems, this resides in
/ENV/bin/, so you can run:
$ source /path/to/ENV/bin/activate
For some shells (e.g. the original Bourne Shell) you may need to use the
. command, when source does not exist. There are also
separate activate files for some other shells, like csh and fish.
bin/activate should work for bash/zsh/dash.
This will change your
$PATH so its first entry is the virtualenv’s
bin/ directory. (You have to use
source because it changes your
shell environment in-place.) This is all it does; it’s purely a
convenience. If you directly run a script or the python interpreter
from the virtualenv’s
bin/ directory (e.g.
/path/to/ENV/bin/python-script.py) there’s no need for
activate script will also modify your shell prompt to indicate
which environment is currently active. To disable this behaviour, see
To undo these changes to your path (and prompt), just run:
On Windows, the equivalent activate script is in the
deactivate to undo the changes.
Based on your active shell (CMD.exe or Powershell.exe), Windows will use either activate.bat or activate.ps1 (as appropriate) to activate the virtual environment. If using Powershell, see the notes about code signing below.
If using Powershell, the
activate script is subject to the
execution policies on the system. By default on Windows 7, the system’s
excution policy is set to
Restricted, meaning no scripts like the
activate script are allowed to be executed. But that can’t stop us
from changing that slightly to allow it to be executed.
In order to use the script, you can relax your system’s execution
AllSigned, meaning all scripts on the system must be
digitally signed to be executed. Since the virtualenv activation
script is signed by one of the authors (Jannis Leidel) this level of
the execution policy suffices. As an administrator run:
PS C:\> Set-ExecutionPolicy AllSigned
Then you’ll be asked to trust the signer, when executing the script. You will be prompted with the following:
PS C:\> virtualenv .\foo New python executable in C:\foo\Scripts\python.exe Installing setuptools................done. Installing pip...................done. PS C:\> .\foo\scripts\activate Do you want to run software from this untrusted publisher? File C:\foo\scripts\activate.ps1 is published by Efirstname.lastname@example.org, CN=Jannis Leidel, L=Berlin, S=Berlin, C=DE, Description=581796-Gh7xfJxkxQSIO4E0 and is not trusted on your system. Only run scripts from trusted publishers. [V] Never run [D] Do not run [R] Run once [A] Always run [?] Help (default is "D"):A (foo) PS C:\>
If you select
[A] Always Run, the certificate will be added to the
Trusted Publishers of your user account, and will be trusted in this
user’s context henceforth. If you select
[R] Run Once, the script will
be run, but you will be prompted on a subsequent invocation. Advanced users
can add the signer’s certificate to the Trusted Publishers of the Computer
account to apply to all users (though this technique is out of scope of this
Alternatively, you may relax the system execution policy to allow running of local scripts without verifying the code signature using the following:
PS C:\> Set-ExecutionPolicy RemoteSigned
activate.ps1 script is generated locally for each virtualenv,
it is not considered a remote script and can then be executed.
Removing an Environment¶
Removing a virtual environment is simply done by deactivating it and deleting the environment folder with all its contents:
(ENV)$ deactivate $ rm -r /path/to/ENV
If you build with
virtualenv --system-site-packages ENV, your virtual
environment will inherit packages from
(or wherever your global site-packages directory is).
This can be used if you have control over the global site-packages directory, and you want to depend on the packages there. If you want isolation from the global system, do not use this flag.
Some paths within the virtualenv are slightly different on Windows: scripts and
executables on Windows go in
ENV\Scripts\ instead of
libraries go in
ENV\Lib\ rather than
To create a virtualenv under a path with spaces in it on Windows, you’ll need the win32api library installed.
Using Virtualenv without
Luckily, it’s easy. You must use the custom Python interpreter to install libraries. But to use libraries, you just have to be sure the path is correct. A script is available to correct the path. You can setup the environment like:
activate_this = '/path/to/env/bin/activate_this.py' execfile(activate_this, dict(__file__=activate_this))
This will change
sys.path and even change
sys.prefix, but also allow
you to use an existing interpreter. Items in your environment will show up
sys.path, before global items. However, global items will
always be accessible (as if the
--system-site-packages flag had been
used in creating the environment, whether it was or not). Also, this cannot undo
the activation of other environments, or modules that have been imported.
You shouldn’t try to, for instance, activate an environment before a web
request; you should activate one environment as early as possible, and not
do it again in that process.
Making Environments Relocatable¶
Note: this option is somewhat experimental, and there are probably caveats that have not yet been identified.
--relocatable option currently has a number of issues,
and is not guaranteed to work in all circumstances. It is possible
that the option will be deprecated in a future version of
Normally environments are tied to a specific path. That means that you cannot move an environment around or copy it to another computer. You can fix up an environment to make it relocatable with the command:
$ virtualenv --relocatable ENV
This will make some of the files created by setuptools use relative paths,
and will change all the scripts to use
activate_this.py instead of using
the location of the Python interpreter to select the environment.
Note: scripts which have been made relocatable will only work if
the virtualenv is activated, specifically the python executable from
the virtualenv must be the first one on the system PATH. Also note that
the activate scripts are not currently made relocatable by
Note: you must run this after you’ve installed any packages into
the environment. If you make an environment relocatable, then
install a new package, you must run
Also, this does not make your packages cross-platform. You can move the directory around, but it can only be used on other similar computers. Some known environmental differences that can cause incompatibilities: a different version of Python, when one platform uses UCS2 for its internal unicode representation and another uses UCS4 (a compile-time option), obvious platform changes like Windows vs. Linux, or Intel vs. ARM, and if you have libraries that bind to C libraries on the system, if those C libraries are located somewhere different (either different versions, or a different filesystem layout).
If you use this flag to create an environment, currently, the
--system-site-packages option will be implied.
This option allows you to provide your own versions of setuptools and/or pip to use instead of the embedded versions that come with virtualenv.
To use this feature, pass one or more
--extra-search-dir options to
virtualenv like this:
$ virtualenv --extra-search-dir=/path/to/distributions ENV
/path/to/distributions path should point to a directory that contains
setuptools and/or pip wheels.
virtualenv will look for wheels in the specified directories, but will use pip’s standard algorithm for selecting the wheel to install, which looks for the latest compatible wheel.
As well as the extra directories, the search order includes:
virtualenv_supportdirectory relative to virtualenv.py
- The directory where virtualenv.py is located.
- The current directory.