8000 FIX: ensure type stability for missing cmaps in `set_cmap` by tacaswell · Pull Request #23785 · matplotlib/matplotlib · GitHub
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FIX: ensure type stability for missing cmaps in set_cmap #23785

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Merged
merged 2 commits into from
Sep 2, 2022
Merged

FIX: ensure type stability for missing cmaps in set_cmap #23785

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0b6b385
FIX: ensure type stability for missing cmaps in `set_cmap`
tacaswell Aug 31, 2022
1f7e0ef
DOC: add note about why we do extra work in this internal function
tacaswell Sep 1, 2022
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8 changes: 5 additions & 3 deletions lib/matplotlib/cm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -701,6 +701,8 @@ def _ensure_cmap(cmap):
"""
if isinstance(cmap, colors.Colormap):
return cmap
return mpl.colormaps[
cmap if cmap is not None else mpl.rcParams['image.cmap']
]
cmap_name = cmap if cmap is not None else mpl.rcParams["image.cmap"]
# use check_in_list to ensure type stability of the exception raised by
# the internal usage of this (ValueError vs KeyError)
_api.check_in_list(sorted(_colormaps), cmap=cmap_name)
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Do you want to put a comment in saying you added this check for error raising type stability so we don't remove it later? Does it need to be sorted or can it be list(_colormaps)?

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The input is used in formatting the error to tell the user what the allowed values are. Given the number of color maps I think sorting is a usability win / kindness for the user to discover what the correct spelling of the color map they tried to ask for is.

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👍 Makes sense. Agreed.

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I pushed a comment about why we are doing extra work.

return mpl.colormaps[cmap_name]
8 changes: 8 additions & 0 deletions lib/matplotlib/tests/test_colors.py
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Expand Up @@ -1543,3 +1543,11 @@ def test_color_sequences():
plt.color_sequences.unregister('rgb') # multiple unregisters are ok
with pytest.raises(ValueError, match="Cannot unregister builtin"):
plt.color_sequences.unregister('tab10')


def test_cm_set_cmap_error():
sm = cm.ScalarMappable()
# Pick a name we are pretty sure will never be a colormap name
bad_cmap = 'AardvarksAreAwkward'
with pytest.raises(ValueError, match=bad_cmap):
sm.set_cmap(bad_cmap)
0