Update python.md (#23669)

* Update python.md

this makes it clear how to alter `attributes` by using `packageOverrides`

* Update python.md

* Update python.md

* Update python.md

* Update python.md

* Update python.md

* Update python.md
This commit is contained in:
Joachim Schiele 2017-03-21 00:06:51 +01:00 committed by GitHub
parent 5e0f932de0
commit 91debcb482

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@ -897,6 +897,27 @@ is executed it will attempt to download the python modules listed in
requirements.txt. However these will be cached locally within the `virtualenv`
folder and not downloaded again.
### How to override a Python package from `configuration.nix`?
If you need to change a package's attribute(s) from `configuration.nix` you could do:
```nix
nixpkgs.config.packageOverrides = superP: {
pythonPackages = superP.pythonPackages.override {
overrides = self: super: {
bepasty-server = super.bepasty-server.overrideAttrs ( oldAttrs: {
src = pkgs.fetchgit {
url = "https://github.com/bepasty/bepasty-server";
sha256 = "9ziqshmsf0rjvdhhca55sm0x8jz76fsf2q4rwh4m6lpcf8wr0nps";
rev = "e2516e8cf4f2afb5185337073607eb9e84a61d2d";
};
});
};
};
};
```
If you are using the `bepasty-server` package somewhere, for example in `systemPackages` or indirectly from `services.bepasty`, then a `nixos-rebuild switch` will rebuild the system but with the `bepasty-server` package using a different `src` attribute. This way one can modify `python` based software/libraries easily. Using `self` and `super` one can also alter dependencies (`buildInputs`) between the old state (`self`) and new state (`super`).
## Contributing