FRidh

Nix guides

Currently the following guides exist:

1. Nix reference guide
2. NixOS reference guide
3. Hydra reference guide
4. Nixpkgs guide

as well as a (mostly outdated) read-only wiki.

FRidh

Python on Nix infrastructure

Introduction

Python is used throughout Nixpkgs. We use it for certain scripts, we provide Python libraries, and we provide applications. There are several methods on how to use Python on Nix, each with their pros and cons. An overview of all issues with the current Python infrastructure on Nix is available in the placeholder issue 1819.

Goal

FRidh

# Produce a list of derivations that should likely have pythonPath set

with import <nixpkgs> {};

with builtins;
let
  # Package set to check
  pythonPackages = pkgs.python2Packages;

  # evaluate expr, returning default on error

FRidh

#! /usr/bin/env python

"""
Filter a .bib file with keys referred to in an .aux file. Print result to STDOUT.
"""

import argparse
import bibtexparser
import re
import itertools

FRidh

{pkgs ? (import <nixpkgs> {})}:

pkgs.stdenv.mkDerivation {
  name = "fetchtarballtest";
  
  src = pkgs.fetchurl {
    url = https://github.com/NixOS/nixpkgs/archive/9c90ff7e7df9ceadc7335bb43cc67ba92e171d53.tar.gz;
    sha256 = "0f8ynrrj24i4g8flp978ccsb2hlwk1n321z8xwj0wakj0ak4c8i9";
  };

FRidh

# Get nix 2.0 image from https://hub.docker.com/r/nixos/nix/
FROM nixos/nix:2.0

# Include the Nix expression we want to build
ADD default.nix default.nix

# We want the possibility for a custom store location
# Note that by using "/" there is effectively no mount namespace
# opening the doors for impurities.
ARG MOUNT_NIX_STORE

FRidh

let
  pkgs = import (fetchTarball channel:nixos-18.03) {};
  custom-store = "/home/freddy/nix_custom_store";
  # Run nix in a mount namespace
  nix-wrapped = pkgs.writeShellScriptBin "nix" ''
    ${pkgs.bubblewrap}/bin/bwrap \
      --unshare-all \
      --proc /proc \
      --dev /dev \
      --tmpfs /run \

FRidh

import os
import subprocess

os.environ["FOO"] = "BAR"

subprocess.run("python3 -c 'import os; print(os.environ.get(\"FOO\", \"\"))'", shell=True)

del os.environ["FOO"]

subprocess.run("python3 -c 'import os; print(os.environ.get(\"FOO\", \"\"))'", shell=True)

FRidh

# # Python package set in Nixpkgs over time
#
# This gist is a Nix expression and generates a figure showing the size
# of the Python package set from September 2015 until now.
#
# To build the figure:
#
#   nix-build

let

FRidh

let
  overlay = self: super: {
    python372 = let
      py = super.python37.override {
        self = py;
        sourceVersion = {
          major = "3";
          minor = "7";
          patch = "2";
          suffix = "";