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FIX: Polar Radial Tick Warnings Labels Bug #31577

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Merged
rcomer merged 9 commits into from
Apr 29, 2026
Merged

FIX: Polar Radial Tick Warnings Labels Bug #31577

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3ac579c
Fix polar RadialLocator triggering spurious UserWarning in set_tickla…
beelauuu Apr 28, 2026
f1e619c
try without?
beelauuu Apr 28, 2026
73c5700
remove warnings
beelauuu Apr 28, 2026
141a625
commit workaround
beelauuu Apr 28, 2026
b0bea47
fix
beelauuu Apr 28, 2026
ad5898f
pyproject toml
beelauuu Apr 28, 2026
e88aad3
remove unneeded test
beelauuu Apr 29, 2026
e8ee14c
linting
beelauuu Apr 29, 2026
1625597
Update test_polar.py
beelauuu Apr 29, 2026
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17 changes: 12 additions & 5 deletions lib/matplotlib/axis.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1999,7 +1999,9 @@ def _set_formatter(self, formatter, level):

if (isinstance(formatter, mticker.FixedFormatter)
and len(formatter.seq) > 0
and not isinstance(level.locator, mticker.FixedLocator)):
and not isinstance(level.locator, mticker.FixedLocator)
and not (hasattr(level.locator, 'base') and
isinstance(level.locator.base, mticker.FixedLocator))):
_api.warn_external('FixedFormatter should only be used together '
'with FixedLocator')

Expand Down Expand Up @@ -2142,16 +2144,21 @@ def set_ticklabels(self, labels, *, minor=False, fontdict=None, **kwargs):
if not labels:
# eg labels=[]:
formatter = mticker.NullFormatter()
elif isinstance(locator, mticker.FixedLocator):
elif (isinstance(locator, mticker.FixedLocator) or
(hasattr(locator, 'base') and
isinstance(locator.base, mticker.FixedLocator))):
# Also handles locators that wrap a FixedLocator (e.g. RadialLocator).
fixed_locator = (locator if isinstance(locator, mticker.FixedLocator)
else locator.base)
# Passing [] as a list of labels is often used as a way to
# remove all tick labels, so only error for > 0 labels
if len(locator.locs) != len(labels) and len(labels) != 0:
if len(fixed_locator.locs) != len(labels) and len(labels) != 0:
raise ValueError(
"The number of FixedLocator locations"
f" ({len(locator.locs)}), usually from a call to"
f" ({len(fixed_locator.locs)}), usually from a call to"
" set_ticks, does not match"
f" the number of labels ({len(labels)}).")
tickd = {loc: lab for loc, lab in zip(locator.locs, labels)}
tickd = {loc: lab for loc, lab in zip(fixed_locator.locs, labels)}
func = functools.partial(self._format_with_dict, tickd)
formatter = mticker.FuncFormatter(func)
else:
Expand Down
10 changes: 10 additions & 0 deletions lib/matplotlib/tests/test_polar.py
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Original file line number Diff line number Diff line change
Expand Up @@ -591,3 +591,13 @@ def test_radial_locator_wrapping():
assert ax.yaxis.isDefault_majloc
assert isinstance(ax.yaxis.get_major_locator(), RadialLocator)
assert isinstance(ax.yaxis.get_major_locator().base, mticker.LogLocator)


def test_set_rticks_ticklabels_no_warning():
# Regression test: RadialLocator wrapping a FixedLocator must not trigger
# the "set_ticklabels() should only be used with a fixed number of ticks"
# UserWarning when set_ticks()/set_rticks() was called first.

fig, ax = plt.subplots(subplot_kw={'projection': 'polar'})
ax.set_rticks([0, 1, 2, 3])
ax.yaxis.set_ticklabels(['zero', 'one', 'two', 'three'])
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