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doc/python: state benefit of fixed point arguments (#537499)

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Johannes Kirschbauer
2026-07-01 19:46:47 +00:00
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parent 17298d28ee 8a2f69744c
commit 587e154b07
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doc/languages-frameworks/python.section.md
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@@ -204,25 +204,9 @@ following are specific to `buildPythonPackage`:
* `setupPyGlobalFlags ? []`: List of flags passed to `setup.py` command.
* `setupPyBuildFlags ? []`: List of flags passed to `setup.py build_ext` command.
##### Using fixed-point arguments {#buildpythonpackage-fixed-point-arguments}
##### Writing override-compatible packages {#buildpythonpackage-fixed-point-arguments}
Both `buildPythonPackage` and `buildPythonApplication` support [fixed-point arguments](#chap-build-helpers-finalAttrs), similar to `stdenv.mkDerivation`.
This allows you to reference the final attributes of the derivation.
Instead of using `rec`:
```nix
buildPythonPackage rec {
pname = "pyspread";
version = "2.4";
src = fetchPypi {
inherit pname version;
hash = "sha256-...";
};
}
```
You can use the `finalAttrs` pattern:
Use `finalAttrs` to make a package easy to update and override:
```nix
buildPythonPackage (finalAttrs: {
@@ -236,7 +220,9 @@ buildPythonPackage (finalAttrs: {
})
```
See the [general documentation on fixed-point arguments](#chap-build-helpers-finalAttrs) for more details on the benefits of this pattern.
When a downstream callsite *overrides* `version` the override becomes visible as `finalAttrs.version`.
Both `buildPythonPackage` and `buildPythonApplication` support [fixed-point arguments](#chap-build-helpers-finalAttrs), similar to `stdenv.mkDerivation`.
::: {.note}