Working directory for Python script

Help
1

With the help of evanjs on IRC, I packaged a simple Python script. It is an IRC welcoming bot. It expects a bot_settings.py file, but I am unable to point it to the file I want. So for import bot_settings as settings it says ModuleNotFoundError: No module named 'bot_settings' in the journal.

Below is the expression. You can see that I also tried makeWrapperArgs.

systemd.services.welcomebot = let welcomebotPkg = pkgs.python38.pkgs.buildPythonPackage rec {
  pname = "welcomebot";
  version = "0.1";
  format = "other";

  src = builtins.fetchGit {
    url = "https://github.com/qarkai/WelcomeBot.git";
    ref = "Py3";
  };
  
  doCheck = false;

  checkInputs = [ pkgs.python38.pkgs.coverage ];

  installPhase = ''
    mkdir -p $out/bin
    install -m0755 bot.py $out/bin/bot.py
  '';
  #makeWrapperArgs = [ "--set PYTHONPATH /home/ircbot:$PYTHONPATH" ];

  meta = {
    description = ''
      IRC bot for welcoming people
    '';
  };

}; in {
    description = "Run WelcomeBot";
    after = [ "network-online.target" ];
    wantedBy = [ "network-online.target" ];
    environment = {
      PYTHONPATH = "/home/ircbot/bot_settings.py:$PYTHONPATH";
      LC_ALL = "en_US.UTF-8";
    };
    serviceConfig = {
      Type = "idle";
      WorkingDirectory = "/home/ircbot";
      ExecStart = "${pkgs.python38}/bin/python3 ${welcomebotPkg}/bin/bot.py";
      User = "ircbot";
      TimeoutStopSec = "3";
      PrivateTmp = "true";
      Restart = "on-failure";
      KillSignal = "SIGINT";        
    };
};
2

Do I interpret correctly that bot_settings.py is supposed to be supplied in the working directory? This cannot work because Python imports relative to the source path, not CWD. You can of course do something like this. For a toy application that is probably good enough.

I just saw the environment settings you have there - pretty sure PYTHONPATH should be a directory, not the file you are targeting.

1 Like
3

Thanks! I went with a “brute force” method proposed by evanjs earlier and it works:

botSettings = pkgs.writeTextFile {
  name = "bot_settings.py";
  text = ''
    ...insert settings here...
  '';
};

installPhase = ''
  mkdir -p $out/bin
  install -m0755 bot.py $out/bin/bot.py
  install -m0755 ${botSettings} $out/bin/bot_settings.py
'';
4

I have a video on python packaging, this may help

However, I would probably use buildPythonApplication, ensure that your “application” works, then reference it in a systemd unit file.

5

Oh, do you have an example of buildPythonApplication and referencing it in a unit? The only info I found about the difference with buildPythonPackage was in an SO comment: “The main difference is that buildPythonApplication doesn’t add the interpreter version to the resulting output name apparently”

6

There’s more to it, it also wont propagate it’s python packages when included as a dependency in another derivation. That way you could have an application packaged with python2 be used in a python3 environment

1 Like
7

Many thanks for all your informative videos :smile:

Not to hijack the thread, but I’m creating a package using buildPythonApplication and was curious about the recommended way to add the directory of the compiled binary to PATH. At the moment, I get the following warning when the package builds:

WARNING: The script MyPythonApp is installed in '/nix/store/blahblahblah-MyPythonApp/bin' which is not on PATH.
  Consider adding this directory to PATH or, if you prefer to suppress this warning, use --no-warn-script-location.
8

you can disregard that. By default, $out/bin is not on the PATH. However, we should probably add --no-warn-script-location to the builder

1 Like
9

I created a PR [staging] python3.pkgs.pipInstallHook: don't warn on script installation by jonringer · Pull Request #104411 · NixOS/nixpkgs · GitHub