Packaging/Python: Difference between revisions

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You can now run <code>nix-shell</code> and it will drop you in a shell similar to the <code>python setup.py develop</code> mode which uses the local code in <tt>./path/to/source</tt> as input. <code>propagatedBuildInputs</code> will contain the packages you need in your project.

After you've finished developing you can replace the relative path with <code>fetchFromGitHub { ... }</code> or <code>[https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/fetchpypi/default.nix fetchPypi] { ... }</code>.

== Testing out a module in a Python shell ==

Once you have your derivation written, you can create a [[Flakes|flake]] to give yourself a shell and easily test out the module you wrote the derivation for.

Create a <code>flake.nix</code> next to your derivation:<syntaxhighlight lang="nix">

{

description = "Dev shell using external derivation";

inputs = {

nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";

flake-utils.url = "github:numtide/flake-utils";

};

outputs = { self, nixpkgs, flake-utils }:

flake-utils.lib.eachDefaultSystem (system:

let

pkgs = import nixpkgs { inherit system; };

# replace ./derivation.nix with the path (relative to this file) to your derivation

mypackage = pkgs.python3Packages.callPackage ./derivation.nix {

lib = pkgs.lib;

};

in {

packages.default = pkgs.python3.withPackages(_: [ mypackage ]);

});

}

</syntaxhighlight>Replace "mypackage" with your package name. Then, run the flake to get into a python REPL with your package, ready to be imported:<syntaxhighlight lang="shell-session">

$ nix run

Python 3.11.10 (main, Sep 7 2024, 01:03:31) [GCC 13.2.0] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>> import mypackage

>>> # test things out...

</syntaxhighlight>

== Pip and Virtualenv enabled nix-shell ==

It might be the case that you simply need to prototype fast small projects with <code>pip</code> and <code>virtualenv</code> without the need for relying on the dependencies being already packaged in nixpkgs.

{{~~Notice~~|Keep in mind that the virtualenv symlinks will be invalidated if you update your system!||

{{Note|Keep in mind that the virtualenv symlinks will be invalidated if you update your system!}}

For a local working python environment you can use the following <code>shell.nix</code><ref>https://groups.google.com/forum/#!topic/nix-devel/3qPfwCAV3GE</ref>.

@@ Line 15: / Line 15: @@
 You can now run <code>nix-shell</code> and it will drop you in a shell similar to the <code>python setup.py develop</code> mode which uses the local code in <tt>./path/to/source</tt> as input. <code>propagatedBuildInputs</code> will contain the packages you  need in your project.
 After you've finished developing you can replace the relative path with <code>fetchFromGitHub { ... }</code> or <code>[https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/fetchpypi/default.nix fetchPypi] { ... }</code>.
+== Testing out a module in a Python shell ==
+Once you have your derivation written, you can create a [[Flakes|flake]] to give yourself a shell and easily test out the module you wrote the derivation for.
+Create a <code>flake.nix</code> next to your derivation:<syntaxhighlight lang="nix">
+{
+  description = "Dev shell using external derivation";
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+        # replace ./derivation.nix with the path (relative to this file) to your derivation
+        mypackage = pkgs.python3Packages.callPackage ./derivation.nix {
+          lib = pkgs.lib;
+        };
+      in {
+        packages.default = pkgs.python3.withPackages(_: [ mypackage ]);
+      });
+}
+</syntaxhighlight>Replace "mypackage" with your package name. Then, run the flake to get into a python REPL with your package, ready to be imported:<syntaxhighlight lang="shell-session">
+$ nix run
+Python 3.11.10 (main, Sep  7 2024, 01:03:31) [GCC 13.2.0] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import mypackage
+>>> # test things out...
+</syntaxhighlight>
 == Pip and Virtualenv enabled nix-shell ==
 It might be the case that you simply need to prototype fast small projects with <code>pip</code> and <code>virtualenv</code> without the need for relying on the dependencies being already packaged in nixpkgs.
-{{Notice|Keep in mind that the virtualenv symlinks will be invalidated if you update your system!||
+{{Note|Keep in mind that the virtualenv symlinks will be invalidated if you update your system!}}
 For a local working python environment you can use the following <code>shell.nix</code><ref>https://groups.google.com/forum/#!topic/nix-devel/3qPfwCAV3GE</ref>.