guix/gnu/packages/aux-files/python/sitecustomize.py
Maxim Cournoyer 874188c0ab
aux-files: sitecustomize: Cleanup and add explanatory comments.
Fixes <https://issues.guix.gnu.org/50105>.

* gnu/packages/aux-files/python/sitecustomize.py: Add a comment explaining the
general idea, and use sys.prefix instead of sys.executable.

(major_minor): Use the unpacking operator (*) to provide the arguments.
(site_packages_prefix): Use os.path.join to form the path.
(python_site): Likewise.  Use sys.prefix instead of sys.executable.
(all_sites_raw): Split on os.path.pathsep.
(sys.path): Directly splice the result in the list.

Suggested-by: Hartmut Goebel <h.goebel@crazy-compilers.com>
Reported-by: Mathieu Othacehe <othacehe@gnu.org>
Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com>
2021-11-11 10:31:32 -05:00

55 lines
2.1 KiB
Python

# -*- coding: utf-8 -*-
# GNU Guix --- Functional package management for GNU
# Copyright © 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com>
#
# This file is part of GNU Guix.
#
# GNU Guix is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or (at
# your option) any later version.
#
# GNU Guix is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
import os
import sys
# Commentary:
#
# Site-specific customization for Guix.
#
# The program below honors the GUIX_PYTHONPATH environment variable to
# discover Python packages. File names appearing in this variable that match
# a predefined versioned installation prefix are added to the sys.path. To be
# considered, a Python package must be installed under the
# 'lib/pythonX.Y/site-packages' directory, where X and Y are the major and
# minor version numbers of the Python interpreter.
#
# Code:
major_minor = '{}.{}'.format(*sys.version_info)
site_packages_prefix = os.path.join(
'lib', 'python' + major_minor, 'site-packages')
python_site = os.path.join(sys.prefix, site_packages_prefix)
try:
all_sites_raw = os.environ['GUIX_PYTHONPATH'].split(os.path.pathsep)
except KeyError:
all_sites_raw = []
# Normalize paths, otherwise a trailing slash would cause it to not match.
all_sites_norm = [os.path.normpath(p) for p in all_sites_raw]
matching_sites = [p for p in all_sites_norm
if p.endswith(site_packages_prefix)]
# Insert sites matching the current version into sys.path, right before
# Python's own site. This way, the user can override the libraries provided
# by Python itself.
sys_path_absolute = [os.path.realpath(p) for p in sys.path]
index = sys_path_absolute.index(python_site)
sys.path[index:index] = matching_sites