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rayosborn opened this issue Apr 3, 2021 · 1 comment
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Invalid backend when importing Matplotlib #19857

rayosborn opened this issue Apr 3, 2021 · 1 comment
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status: duplicate

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@rayosborn
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Bug report

Bug summary

After installing the latest development version on the master branch using pip install . from the cloned Git repository, imports of Matplotlib fail because of an empty backend string ('') when reading rcParamDefaults from a file. If I switch to the 'v3.4.x' branch, there is no problem.

Code for reproduction

>>> import matplotlib

Actual outcome
Using matplotlib-3.4.1.post292+g4085fc7ad

Python 3.8.8 | packaged by conda-forge | (default, Feb 20 2021, 16:12:38) 
[Clang 11.0.1 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import matplotlib
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/rosborn/opt/miniconda3/envs/py38/lib/python3.8/site-packages/matplotlib/__init__.py", line 839, in <module>
    rcParamsDefault = _rc_params_in_file(
  File "/Users/rosborn/opt/miniconda3/envs/py38/lib/python3.8/site-packages/matplotlib/__init__.py", line 773, in _rc_params_in_file
    config[key] = val  # try to convert to proper type or raise
  File "/Users/rosborn/opt/miniconda3/envs/py38/lib/python3.8/site-packages/matplotlib/__init__.py", line 607, in __setitem__
    raise ValueError(f"Key {key}: {ve}") from None
ValueError: Key backend: '' is not a valid value for backend; supported values are ['GTK3Agg', 'GTK3Cairo', 'MacOSX', 'nbAgg', 'Qt4Agg', 'Qt4Cairo', 'Qt5Agg', 'Qt5Cairo', 'TkAgg', 'TkCairo', 'WebAgg', 'WX', 'WXAgg', 'WXCairo', 'agg', 'cairo', 'pdf', 'pgf', 'ps', 'svg', 'template']

Expected outcome
Using matplotlib-3.4.1+5.g272860be0

Python 3.8.8 | packaged by conda-forge | (default, Feb 20 2021, 16:12:38) 
[Clang 11.0.1 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import matplotlib
>>> matplotlib.rcParamsDefault['backend']
'MacOSX'

Matplotlib version

  • Operating system: MacOS v10.15.7
  • Matplotlib version: 3.4.1.post292+g4085fc7ad
  • Matplotlib backend: ? (I can't query it because of the import failure. With v3.4.1, it's 'MacOSX')
  • Python version: 3.8.8

Both versions were installed with pip install . from within the Matplotlib cloned repository, having checked out the master and v3.4.x branches, respectively, for installation within a conda environment.
@rayosborn
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Less than a minute after posting this, I see that #19855 fixes the issue. That's amazingly quick service.

@jklymak jklymak closed this as completed Apr 3, 2021
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@QuLogic @rayosborn @jklymak