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[Bug]: Config directory location finder doesn't account for the home directory being undetermined. #30449
Description
Bug summary
If the home directory cannot be created/written to, matplotlib defaults to creating a temporary folder for its caching/config. However, if the home directory cannot be determined a RunTimeError will be raised.
Code for reproduction
# This will fail on windows
import os
os.environ.pop('HOMEPATH', None)
os.environ.pop('USERPROFILE', None)
import matplotlib
# For linux the following will fail only if the user doesn't exist in the password database
import os
os.environ.pop('HOME', None)
import matplotlibActual outcome
You will get the following error:
File ~\Documents\programming\testing\.venv\Lib\site-packages\matplotlib\__init__.py:1010
1008 rcParams = RcParams() # The global instance.
1009 rcParams._update_raw(rcParamsDefault)
-> 1010 rcParams._update_raw(_rc_params_in_file(matplotlib_fname()))
1011 rcParamsOrig = rcParams.copy()
1012 with _api.suppress_matplotlib_deprecation_warning():
1013 # This also checks that all rcParams are indeed listed in the template.
1014 # Assigning to rcsetup.defaultParams is left only for backcompat.
File ~\Documents\programming\testing\.venv\Lib\site-packages\matplotlib\__init__.py:636, in matplotlib_fname()
633 yield os.path.join(get_configdir(), 'matplotlibrc')
634 yield os.path.join(get_data_path(), 'matplotlibrc')
--> 636 for fname in gen_candidates():
637 if os.path.exists(fname) and not os.path.isdir(fname):
638 return fname
File ~\Documents\programming\testing\.venv\Lib\site-packages\matplotlib\__init__.py:633, in matplotlib_fname.<locals>.gen_candidates()
631 yield matplotlibrc
632 yield os.path.join(matplotlibrc, 'matplotlibrc')
--> 633 yield os.path.join(get_configdir(), 'matplotlibrc')
634 yield os.path.join(get_data_path(), 'matplotlibrc')
File ~\Documents\programming\testing\.venv\Lib\site-packages\matplotlib\__init__.py:340, in _logged_cached.<locals>.wrapper(**kwargs)
338 nonlocal called, ret
339 if not called:
--> 340 ret = func(**kwargs)
341 called = True
342 _log.debug(fmt, ret)
File ~\Documents\programming\testing\.venv\Lib\site-packages\matplotlib\__init__.py:579, in get_configdir()
563 @_logged_cached('CONFIGDIR=%s')
564 def get_configdir():
565 """
566 Return the string path of the configuration directory.
567
(...) 577 directory.
578 """
--> 579 return _get_config_or_cache_dir(_get_xdg_config_dir)
File ~\Documents\programming\testing\.venv\Lib\site-packages\matplotlib\__init__.py:531, in _get_config_or_cache_dir(xdg_base_getter)
529 configdir = Path(xdg_base_getter(), "matplotlib")
530 else:
--> 531 configdir = Path.home() / ".matplotlib"
532 # Resolve the path to handle potential issues with inaccessible symlinks.
533 configdir = configdir.resolve()
File ~\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\pathlib\_abc.py:758, in PathBase.home(cls)
754 @classmethod
755 def home(cls):
756 """Return a new path pointing to expanduser('~').
757 """
--> 758 return cls("~").expanduser()
File ~\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\pathlib\_local.py:808, in Path.expanduser(self)
806 homedir = os.path.expanduser(self._tail[0])
807 if homedir[:1] == "~":
--> 808 raise RuntimeError("Could not determine home directory.")
809 drv, root, tail = self._parse_path(homedir)
810 return self._from_parsed_parts(drv, root, tail + self._tail[1:])
RuntimeError: Could not determine home directory.
Expected outcome
I would expect it to default to creating a temporary directory for the caching and config directories, using them instead.
Additional information
The issue is caused by some calls to Path.home() in _get_config_or_cache_dir.
The simple solution would be to handle the potential RunTimeErrors from the Path.home() calls.
Additionally #12549 would probably also resolve this, bit that seems like a bigger push.
Operating system
Windows
Matplotlib Version
3.10.5
Matplotlib Backend
module://matplotlib_inline.backend_inline
Python version
3.13.7
Jupyter version
No response
Installation
pip
Activity
timhoffm commentedon Aug 21, 2025
This is the appropriate short-term fix.
Logan-Pageler commentedon Aug 22, 2025
Cool thats what I figured. Thanks for the quick reply. I took a crack at implementing that approach #30454
[-][Bug]: Config directory location finder doesnt account for the home directory being undetermined.[/-][+][Bug]: Config directory location finder doesn't account for the home directory being undetermined.[/+]