Commit 146bc8dc authored by Doron Behar's avatar Doron Behar
Browse files

doc/python: document fixed-point arguments (#271387)

parent 7b74e320

doc/languages-frameworks/python.section.md

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@@ -207,6 +207,40 @@ 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}



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:



```nix

buildPythonPackage (finalAttrs: {

  pname = "pyspread";

  version = "2.4";

  src = fetchPypi {

    pname = "pyspread";

    inherit (finalAttrs) version;

    hash = "sha256-...";

  };

})

```



See the [general documentation on fixed-point arguments](#chap-build-helpers-finalAttrs) for more details on the benefits of this pattern.



The [`stdenv.mkDerivation`](#sec-using-stdenv) function accepts various parameters for describing

build inputs (see "Specifying dependencies"). The following are of special

interest for Python packages, either because these are primarily used, or

doc/redirects.json

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@@ -4059,6 +4059,9 @@ 
  "buildpythonpackage-parameters": [

    "index.html#buildpythonpackage-parameters"

  ],

  "buildpythonpackage-fixed-point-arguments": [

    "index.html#buildpythonpackage-fixed-point-arguments"

  ],

  "overriding-python-build-helpers": [

    "index.html#overriding-python-build-helpers"

  ],