virtualenvwrapper.el

A featureful virtualenv tool for Emacs. Emulates much of the functionality of Doug Hellmann's virtualenvwrapper.

Features

• Works with the new python.el, which is the default on Emacs 24.3 and up. Does not support the older python modes.
• Python shells, interactive shells, eshell, and any other subprocesses can be made aware of your virtualenvs.
• Implements a large subset of the functionality of virtualenvwrapper.

Basic Usage

• Obviously make sure you have virtualenv installed. You don't actually need virtualenvwrapper.sh, this is a reimplementation in Emacs lisp.

• Install from MELPA (M-x package-install virtualenvwrapper), or just put virtualenvwrapper.el on your load path somewhere.

• (require 'virtualenvwrapper)
  (venv-initialize-interactive-shells) ;; if you want interactive shell support
  (venv-initialize-eshell) ;; if you want eshell support
  ;; note that setting `venv-location` is not necessary if you
  ;; use the default location (`~/.virtualenvs`), or if the
  ;; the environment variable `WORKON_HOME` points to the right place
  (setq venv-location "/path/to/your/virtualenvs/")

  in your config somewhere.

• Use M-x venv-workon to activate virtualenvs and M-x venv-deactivate deactivate them.

• If you have your virtualenvs spread around the filesystem rather than in one directory, just set venv-location to be a list of paths to each virtualenv. For example:

  (setq venv-location '("/path/to/project1-env/"
                        "/path/to/ptoject2-env/"))

  Notice that the final directory of each path has a different name. The mode uses this fact to disambiguate virtualenvs from each other, so for now it is required.

• You can also change easily the virtual environment location with M-x venv-set-location. This is particularly useful when working with tools such as tox that generate virtual environments dynamically.

What do activating and deactivating actually do?

Many virtual environment support tools describe their functionality as "it just works" or "it's so simple". This is not descriptive enough to figure out what's wrong when something inevitably breaks, so here I will describe exactly what happens when you activate a virtualenv:

1. python-shell-virtualenv-path is set to the virtualenv's directory so that when you open a new python shell, it is aware of the virtual environment's installed packages and modules.
2. The virtualenv's bin directory is prepended to the PATH environment variable so that when a process is launched from Emacs it is aware of any executables installed in the virtualenv (such as nosetests, pep8, etc.). This comes in handy because you can do M-! nosetests to run your tests, for example.
3. The VIRTUAL_ENV environment variable is set to the virtualenv's directory so that any tools that depend on this variable function correctly (one such tool is jedi).
4. The virtualenv's bin directory is added to the exec-path, so that Emacs itself can find the environment's installed executables. This is useful, for example, if you want to have Emacs spawn a subprocess running an executable installed in a virtualenv.
5. gud is configured to run pdb as python -m pdb rather than the default pdb, which is necessary for virtualenvs to be detected.

When you deactivate, all these things are undone. You can safely modify your PATH and exec-path while a virtualenv is active and expect the changes not to be destroyed by deactivating.

This covers everything except interactive shells, which are covered in the next section.

Shells

This thing supports two types of interactive shells, the eshell and the interactive subshell (what you get when you do M-x shell).

Interactive shell

Support for interactive shell is turned on by calling venv-initialize-interactive-shell. After this is done, whenever you call shell, the shell will start in the correct virtualenv. This detects whether or not you have virtualenvwrapper.sh installed and does the right thing in either case. Note that changing the virtualenv in Emacs will not affect any running shells and vice-versa; they are independent processes.

WARNINGS

This feature is a pretty big hack and works by advising the shell function. This works fine if you haven't otherwise tricked out or advised it, but if this is the case it may break. Please file an issue if you encounter any bugs with this functionality, I am interested to see how robust it is.

Eshell

support for eshell is turned on by calling venv-initialize-eshell. After doing this, any new eshells you launch will be in the correct virtualenv and have access to installed executables, etc. The mode also provides a variety of virtualenvwrapper commands that work identically to their bash/zsh counterparts (described in detail below). Note that in contrast to how interactive shells work, Eshell shares an environment with Emacs, so if you activate or deactivate in one, the other is affected as well. Note that this requires the variable eshell-modify-global-environment to be set to true. Running venv-initialize-eshell causes this to occur. If this doesn't work for you, open an issue! It's technically possible to separate the two, but it requires some hacking around with the different namespaces that I won't bother to do unless someone really needs it.

Command Reference

The commands this mode provides are prefixed with venv- All commands can be called interactively using M-x. All of these comamnds have also been aliased without prefixes as eshell functions, so you can call them on the eshell just as you would in bash or zsh. For example:

eshell> workon myenv
eshell> deactivate
eshell> cpvirtualenv env copy
eshell> mkvirtualenv newenv

All will do what would expect.

venv-workon

Prompts for the name of a virtualenv and activates it as described above. Can also be called noninteractively as (venv-workon "name").

When called, it sets gud-pdb-command-name to python -m pdb so that M-x pdb can be used inside the virtual environment.

venv-deactivate

Deactivates your current virtualenv, undoing everything that venv-workon did. This can also be called noninteractively as (venv-deactivate).

When called, it sets gud-pdb-command-name to its default value (usually pdb).

venv-mkvirtualenv

Prompt for a name and create a new virtualenv. If your virtualenvs are all kept in the same directory (i.e. venv-location is a string), then the new virtualenv will be created in that directory. If you keep your virtualenvs in different places (i.e. venv-location is a list), then the new virtualenv will be created in the current default directory. Also callable noninteractively as (venv-mkvirtualenv "name").

venv-mkvirtualenv-using

Supplying a prefix command (C-u) to venv-mkvirtualenv will prompt for a Python interpreter to use. You can use this function to specify the interpreter noninteractively.

venv-rmvirtualenv

Prompt for the name of a virutalenv and delete it. Also callable noninteractively as (venv-rmvirtualenv "name").

venv-lsvirtualenv

Display all available virtualenvs in a help buffer. Also callable noninteractively as (venv-list-virtualenvs).

venv-cdvirtualenv

Change the current default directory to the current virtualenv's directory. If called noninteractively, you can optionally provide an argument, which is interpreted as a subdirectory. For example, to go to the bin directory of the currently active virtualenv, call (venv-cdvirtualenv "bin").

venv-cpvirtualenv

Makes a new virtualenv that is a copy of an existing one. Prompts for the names of both. WARNING This comes with the same caveat as the corresponding command in the original virtualenvwrapper, which is that some packages hardcode their locations when being installed, so creating new virtualenvs in this manner may cause them to break. Use with caution.

Useful Macros

There is a venv-with-virtualenv macro, which takes the name of a virtualenv and then any number of forms and executes those forms with that virtualenv active, in that virtualenv's directory. For example:

(venv-with-virtualenv "myenv" (message default-directory))

Will message the path of myenv's directory. There's also a venv-all-virtualenv macro, which takes a series of forms, activates each virtualenv in turn, moves to its directory, and executes the given forms.

Since it's common to want to execute shell commands, there are convenience macros, venv-with-virtualenv-shell-command and venv-allvirtualenv-shell-command, which take a string, interpreted as a shell command, and do exactly what you'd expect. So for example, you can do (venv-allvirtualenv-shell-command "pip install pep8") to install pep8 in all virtualenvs. venv-allvirtualenv-shell-command can also be called interactively and will prompt for a command to run if so.

The eshell supports using this command just like in bash or zsh, so at an eshell prompt, you can just do:

eshell> allvirtualenv pip install pep8

And it will do what you expect.

Extras

This mode doesn't screw with things you probably have customized yourself, such as your mode line, keybindings, mode-hooks, etc. in order to provide stuff like automatically turning on virtualenvs in certain projects, show the virtualenv on the mode line, etc. Instead, you can do all these things pretty easily using tools already provided by Emacs. How to do some of them are described below.

Keybindings

This mode doesn't provide any. I don't presume to know how you want your keybindings, you can bind them to whatever you want! Go crazy!

Hooks

Virtualenvwrapper lets you write shell scripts that run as hooks after you take certain actions, such as creating or deleting a virtualenv. This package provides Emacs hooks, to achieve the same thing. The complete list of hooks is:

venv-premkvirtualenv-hook
venv-postmkvirtualenv-hook
venv-prermvirtualenv-hook
venv-postrmvirtualenv-hook
venv-preactivate-hook
venv-postactivate-hook
venv-predeactivate-hook
venv-postdeactivate-hook

each of which is run when you would expect based on the name.

For example, to install commonly used packages when a new virtualenv is created you could modify the venv-postmkvirtualenv-hook as follows:

(add-hook 'venv-postmkvirtualenv-hook
          (lambda () (shell-command "pip install nose flake8 jedi")))

Automatically activating a virtualenv in a particular project

It's also common to want to have a virtualenv automatically activated when you open a file in a certain project. This mode provides no special way to do this because once again Emacs has already done it in the form of per-directory local variables. In order to have a virtualenv automatically activated when you open a python file in a particular project, you could put a .dir-locals.el in the project's root directory with something like:

((python-mode . ((eval . (venv-workon "myproject-env")))))

Automatically activating a virtualenv when using projectile

If you're using projectile there's an easier way to automatically activate a virtualenv when entering a project.

You just have to call (venv-projectile-auto-workon) after switching projects, this can be achieved hooking the call to the action projectile-switch-project-action like this:

(setq projectile-switch-project-action 'venv-projectile-auto-workon)

If you relay on another use for this action, then just add a lambda instead:

(setq projectile-switch-project-action
      '(lambda ()
         (venv-projectile-auto-workon)
         (projectile-find-file)))

As long as a virtualenv is found in the projectile-project-root and whose name is in the list venv-dirlookup-names it will be automatically activated. By default, it's value is '(".venv", "venv")', but you can set if however you like to match your naming conventions:

(setq venv-dirlookup-names '(".venv" "pyenv" ".virtual"))

You can add as many names you need, the first one found in the current project will be activated.

Displaying the currently active virtualenv on the mode line

The name of the currently active virtualenv is stored in the variable venv-current-name. If you want to have it displayed on your custom mode line you can just add (:exec (list venv-current-name))) somewhere in your mode-line-format. If you don't customize your mode line and just want to have the current virtualenv displayed, you can do:

(setq-default mode-line-format (cons '(:exec venv-current-name) mode-line-format))

Eshell prompt customization

You also might want to have the name of your current virtualenv appear on the eshell prompt. You can do this by a pretty similar mechanism, just include venv-current-name in your eshell-prompt-function somewhere. Here is a simple example of a prompt that includes the current virtualenv name followed by a dollar sign:

(setq eshell-prompt-function
    (lambda ()
      (concat venv-current-name " $ ")))

Make sure you also adjust your eshell-prompt-regexp if you do this.

More about customizing the eshell prompt on the EmacsWiki.

Bugs / Comments / Contributions

Open an issue or a PR! I'm happy to pull in contributions or take suggestions for improvements.

Hacking

I use Cask to manage dependencies and ert-runner for testing. To get started:

1. install cask
2. Install dependacies with cask install --dev
3. Verify that the tests pass with cask exec ert-runner

The tests are pretty rudimentary integration tests but they verify that all the basic functionality works.

If you're planning on submitting a PR, please make sure that the tests pass before you do so. Thanks!

License

Copyright (C) 2013 James J. Porter

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.