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https://github.com/nix-community/pypi2nix
Abandoned! Generate Nix expressions for Python packages
https://github.com/nix-community/pypi2nix
abandoned nix python
Last synced: about 1 month ago
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Abandoned! Generate Nix expressions for Python packages
- Host: GitHub
- URL: https://github.com/nix-community/pypi2nix
- Owner: nix-community
- Archived: true
- Created: 2012-05-12T22:05:40.000Z (over 12 years ago)
- Default Branch: master
- Last Pushed: 2021-04-01T10:01:11.000Z (over 3 years ago)
- Last Synced: 2024-09-24T01:04:49.648Z (about 1 month ago)
- Topics: abandoned, nix, python
- Language: Python
- Homepage:
- Size: 32.1 MB
- Stars: 194
- Watchers: 6
- Forks: 47
- Open Issues: 62
-
Metadata Files:
- Readme: README.rst
Awesome Lists containing this project
README
pypi2nix - generate Nix expressions for Python packages
=======================================================
.. contents::
See https://pypi2nix.readthedocs.io/en/latest/ for documentation.
.. inclusion-marker
``pypi2nix`` is a command line tool that generates `Nix expressions`_ from
different ``requirements.txt``. This is useful for:
- Building a Nix derivation for a program written in Python as part of
packaging it.
- Setting up a development environment to hack on a program written in Python.
The only way we can fix bugs with pypi2nix is if you report them. Please
create an issue if you discover problems.
``pypi2nix`` will (until further notice) only work with latest *unstable*
channel. This is due to ongoing changes in Python infrastructure happening in
Nixpkgs.
The `Nixpkgs manual section about Python
`_ makes good reading if you
haven't seen it already.
1. Installation
---------------
``pypi2nix`` is part of ``nixpkgs``. If you just want to use
``pypi2nix`` on your system, it is recommended that you install it via
the regular means, e.g. ``nix-env -iA nixos.pypi2nix`` on NixOS or
``nix-env -iA nixpkgs.pypi2nix`` on other systems utilizing nix.
System Requirements
^^^^^^^^^^^^^^^^^^^
Make sure Nix is installed::
% curl https://nixos.org/nix/install | sh
Currently ``pypi2nix`` is only tested against ``linux`` systems.
Supported ``nixpkgs`` channels are ``nixos-19.09`` and
``nixos-unstable``. Due to the nature of ``nixos-unstable`` the
occasional breakage of ``pypi2nix`` is to be expected. We try to
provide fixes in that regard in a timely manner.
Ad hoc Installation (Simple)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
For just installing the package with a command, use `nix-env`_::
nix-env -if https://github.com/nix-community/pypi2nix/tarball/master
Declarative Installation (Advanced)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If you prefer to explicitly declare each installed package in your
Nix(OS) or project configuration, you can do the following:
First, import the package from its ``default.nix`` by fetching the
whole git repository with ``pkgs.fetchgit``. Afterwards you can just
add the imported attribute the list of installed software.
Below you find an example for NixOS' ``configuration.nix``. Other
methods like `home-manager`_ work similar::
let
pypi2nix = import (pkgs.fetchgit {
url = "https://github.com/nix-community/pypi2nix";
# adjust rev and sha256 to desired version
rev = "v2.0.1";
sha256 = "sha256:0mxh3x8bck3axdfi9vh9mz1m3zvmzqkcgy6gxp8f9hhs6qg5146y";
}) {};
in
environment.systemPackages = [
# your other packages
pypi2nix
];
2. Usage
--------
The easiest way to generate a Nix expressions is to invoke::
% pypi2nix -e packageA -e packageB==0.1
If you also have a ``requirements.txt`` file for your Python project you can use
the ``-r`` option.
::
% pypi2nix -e packageA -e packageB==0.1 \
-r requirements.txt -r requirements-dev.txt
What is being generated
^^^^^^^^^^^^^^^^^^^^^^^
Option ``-V`` tells pypi2nix which python version to be used. To see which
Python versions are available consult ``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 your pypi2nix call.
This is the output you would expect from ``pip freeze``.
- ``requirements.nix`` is a file which contains a nix expression to for the package set that was built.
- ``requirements_override.nix`` - this is an empty file which lets you
override generated nix expressions.
Building generated packages
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Build one package::
% nix build -f requirements.nix packages.empy
Build all packages::
% nix build -f requirements.nix packages
Build python interpreter with all packages loaded::
% nix build -f requirements.nix interpreter
% ./result/bin/python -c "import empy"
Enter development environment::
% nix run -f requirements.nix interpreter
[user@localhost:~/dev/nixos/pypi2nix) % python -c "import empy"
Using generated packages
^^^^^^^^^^^^^^^^^^^^^^^^
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.""``. If
you want to depend on *all* packages you can even do::
propagatedBuildInputs = builtins.attrValues python.packages;
Command line options
^^^^^^^^^^^^^^^^^^^^
``-v``
Increase amount and detail of information output to the user.
Verbosity levels are ``ERROR``, ``WARNING``, ``INFO`` and
``DEBUG`` in that order. The default verbosity is ``INFO``.
``-q``
Reduce amount and detail of information output to the user. See
``-v`` for more information.
``-I/--nix-path TEXT``
Add entries to the ``NIX_PATH`` environment variable similarly to
how ``-I`` works with ``nix`` executables like ``nix-build``.
This can be useful for generating package sets based on a
different ``nixpkgs`` version than the one used one the local
system.
``--nix-shell PATH``
Path to an alternative version of the ``nix-shell`` command. The
default is the first executable that will be found in the current
``PATH`` of the system.
``--version``
Show the current version of ``pypi2nix``
``--basename TEXT``
This option determins the name the produced files. So with
``--basename environment`` you would get the files
``environment.nix``, ``environment_frozen.nix`` and
``environment_override.nix``.
``--extra-build-inputs/-E TEXT``
Extra build inputs that the required python packages need to run,
e.g. ``libffi`` or ``libgl``. In that case you would provide ``-E
"libffi libgl"``. These nix packages will be available in the
build environment for the wheels.
``--emit-extra-build-inputs/--no-emit-extra-build-inputs``
These options let you control if external build dependencies
specified via ``-E`` will end up in the generated nix package set.
Please note that if you select this option, your overrides need to
make sure that python packages find their respective external
dependencies.
``--extra-env/-N TEXT``
Extra environment variables that will be passed to the build
environment. Note that you can use nix expressions in this
string, e.g. ``-N 'BERKELEYDB_DIR=${pkgs.db.dev}'``.
``--enable-tests/-T``
Specify this flag if you want to enable the check phase of all
packages in the generated nix expression. Please note that this
feature is highly exprimental and will probably not work for your
use case.
``--python-version/-V``
Specify the python version you want the requirement set to be
built with. The default is ``3`` which translates to the
``python3`` derivation of ``nixpkgs``.
``--requirements/-r FILE``
Specify a requirements file, similar as you would with ``pip``.
``pypi2nix`` tries to be fully compatible with the file format of
``pip``.
``--editable/-e TEXT``
This option allows you to specify individual requirements that get
added to the requirement set, e.g. ``pypi2nix -e attrs``,
``pypi2nix -e $HOME/src/myproject#egg=myproject`` or ``pypi2nix -e .#egg=myegg``.
``--setup-requires/-s TEXT``
Allows you to specify python packages that need to be present in
the build environment of other packages, a good example of this
would be ``setuptools-scm``. Note that ``pypi2nix`` tries to
detect these dependencies on its own. You only need to specify
this flag in cases where a package author or maintainer forgot to
mention build time dependencies in their setup or neither
``setup.cfg`` nor ``pyproject.toml`` is used.
``--overrides/-O URL``
Allows you to specify additional overrides that conform to the
general structure of ``requirements_override.nix``. We support
regular URLs with ``http`` and ``https`` scheme and also ``git``.
An example for using ``https`` would be ``pypi2nix -O
https://myoverrides.test/overrides.nix``. Reusing an overlay from
a git repository would be done like so: ``pypi2nix -O
git+https://github.com/nix-community/pypi2nix.git&path=requirement_override.nix``.
Please keep in mind that these overrides are incorporated in a nix
expression with a precalculated hash value. So if the file
changes upstream your generated package can not be built anymore.
``--default-overrides/--no-default-overrides``
Pull in overrides from
``https://github.com/nix-community/pypi2nix-overrides``. This
feature is enabled by default.
``--wheels-cache/-W TEXT``
A location where prebuilt wheels can be found. This option will
ultimately be passed to ``pip --find-links``. Only point to
wheels that are built through ``pypi2nix`` on your own or a very
similar system.
``--build-directory TEXT``
**Warning** A bug in ``pypi2nix`` currently prevents some packages
from being built with this option set. It is recommended to not
use this flag.
The directory where pypi2nix would build the python environment to
generate the desired nix expression. If not specified, the build
directory will be temporary and is deleted before the program
exits.
``--dependency-graph-output PATH``
Output the dependency information of processed packages to the
specified path. The output format is yaml.
3. When it doesn't work
-----------------------
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.
Sometimes ``pypi2nix`` fails entirely. If this happens, open a bug --
it's almost always a bug in ``pypi2nix``. However, sometimes
``pypi2nix`` succeeds but the resulting ``requirements.nix`` file
fails during the building of your Python package. Depending on what
the problem is, this section may be helpful.
Non-Python/system dependencies
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Quite a few Python packages require non-Python dependencies to be
present at build time. These packages will fail to build with error
messages about not being able to find ``foo.h`` or some ``fooconfig``
file. To work around this, ``pypi2nix`` has ``-E`` options which can
be used to include extra non-Python dependencies.
For example, ``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
Additional environment variables
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Some packages expect additional environment variables to be set::
% pypi2nix -v -V 2.7 -e bsddb3 -N 'BERKELEYDB_DIR=${pkgs.db.dev}'
Using requirements_override.nix
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Some other failures might be caused because the derivation that
``pypi2nix`` wrote was incomplete. A very common situation is that
``pypi2nix`` didn't include all the dependencies of some package. As
an example, ``execnet`` depends on ``setuptools-scm``, but
``pypi2nix`` may not detect this.
When this happens, Nix will fail to build ``execnet``, perhaps with an
error message from distutils/setuptools complaining that it can't find
a distribution for ``setuptools-scm``. What's happening here is that
normally ``execnet`` would fetch ``setuptools-scm`` from PyPI, but Nix
disables network access to guarantee reproducability. So when you
build ``execnet``, it fails to find ``setuptools-scm``.
For these situations, ``pypi2nix`` provides a
``requirements_override.nix`` file, which lets you override anything
that it generated. You can even add new packages to the dependency set
this way.
As an example, let's add ``setuptools-scm`` as a build-time dependency
of ``execnet``. Here's the ``requirements_override.nix``::
{ pkgs, python }:
self: super: {
"execnet" = python.overrideDerivation super."execnet" (old: {
buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
});
}
In a similar way, you can add or remove any Python package.
Shared overrides
^^^^^^^^^^^^^^^^
In addition to the empty autogenerated ``requirements_overrides.nix``
file, you can include pre-existing overrides files. These overrides
will be included the same way as your ``requirements_overrides.nix``.
The ``pypi2nix`` author also maintains a set of "default" overrides at
https://github.com/nix-community/pypi2nix-overrides/blob/master/overrides.nix --
you can include these by using the ``--default-overrides`` argument to
``pypi2nix``. These overrides are designed in such a way that they
only override dependencies that were already present in your
``requirements.nix``.
You can also include an overrides file using the ``-O`` command line
argument. ``pypi2nix`` can fetch these overrides from a local file or
over certain common protocols.
``http`` and ``https``
``pypi2nix --overrides https://raw.githubusercontent.com/nix-community/pypi2nix-overrides/master/overrides.nix``
Note that the generated Nix expression will check if contents of
the overrides file differs from when the Nix expression was built, and
fail if this was the case (or the file does not exist anymore).
Local files
``pypi2nix --override ../some/relative/path --override /some/absolute/path``
Git repositories
``pypi2nix --override git+https://github.com/nix-community/pypi2nix.git#path=overrides.nix``
If you want to import a file from a specific git repository you have
to prefix its URL with ``git+``, quite similar to how you would do
in a ``requirements.txt`` file for ``pip``.
4. Advanced Use
---------------
Creating default.nix for your project
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Nothing speaks better than an example::
{ }:
let
pkgs = import {};
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 all the packages generated by
``pypi2nix`` as well as some common utilities.
To create a package you use ``python.mkDerivation`` which works like
the ``pythonPackages.buildPythonPackage`` function in ``nixpkgs``. All
generated packages are available as one attribute set under
``python.packages``.
.. TODO explain withPackages and show some example
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``.
Convert generated requirements.nix into nixpkgs overlay
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
A working example is worth 1000 words.
overlay.nix::
self: super:
{
customPython =
(import ./requirements.nix { pkgs = self; });
}
shell.nix::
with (import { overlays = [ (import ./overlay.nix) ]; });
customPython.interpreter
.. _`Nix expressions`: http://nixos.org/nix/manual/#chap-writing-nix-expressions
.. _`examples/Makefile`: https://github.com/nix-community/pypi2nix/blob/master/examples/Makefile
.. _`nix-env`: http://nixos.org/nix/manual/#sec-nix-env
.. _`home-manager`: https://github.com/rycee/home-manager