pyrox.dev
1"""
2This is a Nix-specific module for discovering modules built with Nix.
3
4The module recursively adds paths that are on `NIX_PYTHONPATH` to `sys.path`. In
5order to process possible `.pth` files `site.addsitedir` is used.
6
7The paths listed in `PYTHONPATH` are added to `sys.path` afterwards, but they
8will be added before the entries we add here and thus take precedence.
9
10Note the `NIX_PYTHONPATH` environment variable is unset in order to prevent leakage.
11
12Similarly, this module listens to the environment variable `NIX_PYTHONEXECUTABLE`
13and sets `sys.executable` to its value.
14"""
15import site
16import sys
17import os
18import functools
19
20paths = os.environ.pop('NIX_PYTHONPATH', None)
21if paths:
22 functools.reduce(lambda k, p: site.addsitedir(p, k), paths.split(':'), site._init_pathinfo())
23
24# Check whether we are in a venv or virtualenv.
25# For Python 3 we check whether our `base_prefix` is different from our current `prefix`.
26# For Python 2 we check whether the non-standard `real_prefix` is set.
27# https://stackoverflow.com/questions/1871549/determine-if-python-is-running-inside-virtualenv
28in_venv = (sys.version_info.major == 3 and sys.prefix != sys.base_prefix) or (sys.version_info.major == 2 and hasattr(sys, "real_prefix"))
29
30if not in_venv:
31 executable = os.environ.pop('NIX_PYTHONEXECUTABLE', None)
32 prefix = os.environ.pop('NIX_PYTHONPREFIX', None)
33
34 if 'PYTHONEXECUTABLE' not in os.environ and executable is not None:
35 sys.executable = executable
36 if prefix is not None:
37 # Sysconfig does not like it when sys.prefix is set to None
38 sys.prefix = sys.exec_prefix = prefix
39 site.PREFIXES.insert(0, prefix)