Nix + Python

Note

Be aware that this code is still in very experimental.

Tools in this repository should provide better way to work with Python and Nix.

End goal is to replace virtualenv and provide better build time isolation then virtualenv does, while still having the possibility to use tools that python developers are familiar with (eg pip, easy_install, buildout, ...).

Contents

• Why? Isn't virtualenv enough?
• How to install it?
• How to use it?
• How it works?
• Things that don't work (yet)
• Found bugs?

Why? Isn't virtualenv enough?

No. Well at least not for me :)

Well to be honest virtualenv does the job that it promises, but many times this is not enough. Many times system packages are needed to be able to install specific python packages, eg. lxml, Pillow, ...

And nix-virtualenv can install system packages (even MySQL or PostgreSQL).

How to install it?

1. Make sure Nix is installed:

   % curl https://nixos.org/nix/install | sh
   

or follow the manual.

2. Clone this repository and place bin/ folder of this repository to $PATH. eg.::

   % git clone git://github.com/garbas/nix-virtualenv
   % echo "export PATH=`pwd`/nix-virtualenv/bin:\$PATH" >> ~/.profile
   

How to use it?

To install packages::

~ % ./bin/nix-virtualenv-py27 examples
...
(nix-shell) ~/examples % pip install pyramid
... or ...
(nix-shell) ~/examples % easy_install pyramid
... or ...
(nix-shell) ~/examples % buildout -c buildout.cfg

To start working on python package::

(nix-shell) ~/examples % python setup.py develop --prefix $PYTHONPREFIX

To install other packages from nixpkgs you can pass them via -p parameter:

% ./bin/nix-virtualenv-py27 examples -p lxml -p postgresql
(nix-shell) ~/examples % which psql
/nix/store/...-postgresql-9.2.10/bin/psql
(nix-shell) ~/examples % python -c "import lxml; print lxml.__file__"
/nix/store/...-python2.7-lxml-3.3.6/lib/python2.7/site-packages/lxml/__init__.pyc

Can virtualenv do this? :)

How it works?

There are few scripts inside bin folder in this repository starting with the name nix-virtualenv. You can use this scripts to create python environment as you would with virtualenv.

After running any of the nix-virtualenv-pyXX script use buildout, pip and easy_install as you're used.

TODO: explain how internals work once implementations settles

Things that don't work (yet)

• TODO: python setup.py develop should use --prefix without specifying it
• BUG: pip --editable tries to install into /nix/store/...
• BUG: pip --upgrade does not work since it tries to upgrade package in place, which is in /nix/store/...
• TODO: patch tox to use nix-virtualenv instead of virtualenv. https://bitbucket.org/hpk42/tox/src/master/tox/_venv.py?at=default#cl-174

Found bugs?

Report them to issue tracker:

https://github.com/garbas/nix-virtualenv/issues

or ping me on IRC

garbas on freenode.net