pypi2nix is a command line tool that generates Nix expressions from
different python specific sources (requirements.txt, buildout.cfg,
...).
The only way I can fix bugs with pypi2nix is if you report them. Ping me @garbas if you get stuck.
pypi2nix will (until further notice) only work with latest unstable
channel. This is due to ongoing change in python infrastructure happening this
year.
Contents
Make sure Nix is installed.:
% curl https://nixos.org/nix/install | sh
Next clone pypi2nix repository.:
% git clone https://github.com/garbas/pypi2nix
And now install it using nix-env command.:
% cd pypi2nix % nix-env -f release.nix -iA build."x86_64-linux"
The easiest way to generate a Nix expressions is to invoke.:
% pypi2nix -V "3.5" -e packageA -e packageB==0.1
If you also have requirements.txt file for you python project you can use
-r option.:
% pypi2nix -V "3.5" -e packageA -e packageB==0.1 \
-r requirements.txt -r requirements-dev.txt
If your project relies on zc.buildout you can give -b option a try.:
% pypi2nix -V "2.7" -b buildout.cfg
Option -V tells pypi2nix which python version to be used. To see which
python versions are available consule pypi2nix --help.
Once Nix expressions are generated you should be able to see 3 new files:
requirements_frozen.txt- full frozen set for your for you pypi2nix call. This is the output you would expect from pip freeze.requirements.nixis a file which contains a nix expression to for the package set that was built.requirements_override.nix- this is an empty file which is ment to override generated nix expressions.
Quite few python package require non-python dependencies to be present at
installation time. For this purpose pypi2nix has -E options which can
be used to define this extra non-python dependencies.
psycopg2 requires pg_config binary to be present at installation time:
% pypi2nix -v -V 2.7 -e psycopg2 -E postgresql
lxml requires libxml2 and libxslt system package:
% pypi2nix -v -V 2.7 -e lxml -E libxml2 -E libxslt
Build one package:
% nix-build requirements.nix -A packages.empy
Build all packages:
% nix-build requirements.nix -A packages
Build python interpreter with all packages loaded:
% nix-build requirements.nix -A interpreter % ./result/bin/python -c "import empy"
Enter developent environemnt:
% nix-shell requirements.nix -A interpreter (nix-shell) % python -c "import empy"
If you are working on a project where its dependencies are defined in
requirements.txt then you can create a default.nix and add generated
packages as buildInputs as demonstrated here:
{}:
let
python = import ./requirements.nix { inherit pkgs; };
in python.mkDerivation {
name = "ProjectA-1.0.0";
src = ./.;
buildInputs = [
python.packages."coverage"
python.packages."flake8"
python.packages."mock"
python.packages."pytest"
python.packages."pytest-asyncio"
python.packages."pytest-cov"
python.packages."pytest-mock"
python.packages."pytest-xdist"
python.packages."virtualenv"
];
propagatedBuildInputs = [
python.packages."aiohttp"
python.packages."arrow"
python.packages."defusedxml"
python.packages."frozendict"
python.packages."jsonschema"
python.packages."taskcluster"
python.packages."virtualenv"
];
...
}
As you can see you can access all packages via python.packages."<name>". If
you want to depend on all packages you can as well do:
propagatedBuildInputs = builtins.attrValues python.packages;
I hope nobody is expecting pypi2nix to do always a perfect job. In python
packaging there are just too many different cases that we will never be able to
cover. What pypi2nix tries to do is to get you very close.
When things go not as you expected, pypi2nix gives you an option to
override anything that it was generated. Even add new packages this way.
An example how you would override a derivation would be adding extra build time
dependencies which we can not detect with pypi2nix. As example lets add
setuptools-src which got generated, but was not detected as build time
dependency of execnet:
{ pkgs, python }:
self: super: {
"execnet" = python.overrideDerivation super."execnet" (old: {
buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
});
}
This was you can add or remove any python package.
Nothing speaks better then an example:
{ }:
let
pkgs = import <nixpkgs> {};
python = import ./requirements.nix { inherit pkgs; };
in python.mkDerivation {
name = "projectA-1.0.0";
src = ./.;
buildInputs = [
python.packages."coverage"
python.packages."flake8"
python.packages."mock"
python.packages."pytest"
python.packages."pytest-asyncio"
python.packages."pytest-cov"
python.packages."pytest-mock"
python.packages."pytest-xdist"
];
propagatedBuildInputs = [
python.packages."aiohttp"
python.packages."arrow"
python.packages."defusedxml"
python.packages."frozendict"
python.packages."jsonschema"
];
checkPhase = ''
export NO_TESTS_OVER_WIRE=1
export PYTHONDONTWRITEBYTECODE=1
flake8 src/
py.test --cov=src -cov-report term-missing
coverage html
'';
}
Important to know here is that you instantiate all generated packages as
python = import ./requirements.nix { inherit pkgs; }; which gives you
a python environment with pypi2nix generated packages and some common
utilities.
To create a package you would use python.mkDerivation as you are used to
that pythonPackages.buildPythonPackage function in nixpkgs. All
generated packages are available as one attribute set under
python.packages.
One of future goals of pypi2nix project is to also improve the UX of our
python tooling in nixpkgs. While this is very hard to do within nixpkgs it
is almost trivial to experiment with this outside nixpkgs.
The file examples/Makefile contains specific instructions for packages like
sentry, empy, lektor, awscli and rss2email.
Clone pypi2nix repository and using nix-shell command enter development environment.:
% git clone https://github.com/garbas/pypi2nix % cd pypi2nix % nix-shell
Code is located in src/pypi2nix.