build-system/python: Install to the python output if present.

* gnu/build/python-build-system.scm (python-output): New procedure.
  (site-packages, install): Use python-output to find the output path.
  (wrap, rename-pth-file): Use site-packages where appropriate.
* doc/guix.texi (Build Systems): Mention the new behavior.

1 files changed, 7 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 5b854ccbd4..59085b6afd 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -6685,6 +6685,13 @@ By default guix calls @code{setup.py} under control of
 @code{setuptools}, much like @command{pip} does.  Some packages are not
 compatible with setuptools (and pip), thus you can disable this by
 setting the @code{#:use-setuptools?} parameter to @code{#f}.
+
+If a @code{"python"} output is available, the package is installed into it
+instead of the default @code{"out"} output. This is useful for packages that
+include a Python package as only a part of the software, and thus want to
+combine the phases of @code{python-build-system} with another build system.
+Python bindings are a common usecase.
+
 @end defvr
 
 @defvr {Scheme Variable} perl-build-system