reproducible python environment with nix

shell.nix

{ pkgs ? import <nixpkgs> {} }:

let
  mach-nix = import (builtins.fetchGit {
    url = "https://github.com/DavHau/mach-nix";
    ref = "refs/tags/3.3.0";
    }) {
      pkgs = pkgs;
      python = "python37";
      pypiDataRev = "48f4b1841d11673822d3f42178480378d1a07a90"; # 2021-09-27T20:16:37Z
      pypiDataSha256 = "0iallhbxsa3gmgby3rrfhz1a3yq9pdyakrk0p6036spyhig8p4bh";
  };

  customPython = mach-nix.mkPython {
    requirements = builtins.readFile ./requirements.txt;
  };
in

pkgs.mkShell {
  buildInputs = [ customPython ];
  shellHook = ''
  alias vim='nvim'
  '';
}