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Clarify error for colorbar with unparented mappable #23740

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Merged
merged 1 commit into from
Aug 26, 2022
Merged

Clarify error for colorbar with unparented mappable #23740

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5 changes: 4 additions & 1 deletion doc/api/next_api_changes/removals/22081-AL.rst
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Original file line number Diff line number Diff line change
@@ -1,7 +1,10 @@
colorbar defaults to stealing space from the mappable's axes rather than the current axes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Pass ``ax=plt.gca()`` to restore the previous behavior.
If the mappable does not have an Axes, then an error will be raised.

Pass the *cax* or *ax* argument to be explicit about where the colorbar will be
placed. Passing ``ax=plt.gca()`` will restore the previous behavior.

Removal of deprecated ``colorbar`` APIs
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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8 changes: 7 additions & 1 deletion lib/matplotlib/figure.py
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Expand Up @@ -1245,13 +1245,19 @@ def colorbar(
"""

if ax is None:
ax = getattr(mappable, "axes", self.gca())
ax = getattr(mappable, "axes", None)

if (self.get_layout_engine() is not None and
not self.get_layout_engine().colorbar_gridspec):
use_gridspec = False
# Store the value of gca so that we can set it back later on.
if cax is None:
if ax is None:
raise ValueError(
'Unable to determine Axes to steal space for Colorbar. '
'Either provide the *cax* argument to use as the Axes for '
'the Colorbar, provide the *ax* argument to steal space '
'from it, or add *mappable* to an Axes.')
current_ax = self.gca()
userax = False
if (use_gridspec and isinstance(ax, SubplotBase)):
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10 changes: 9 additions & 1 deletion lib/matplotlib/tests/test_colorbar.py
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Expand Up @@ -315,6 +315,14 @@ def test_colorbarbase():
Colorbar(ax, cmap=plt.cm.bone)


def test_parentless_mappable():
pc = mpl.collections.PatchCollection([], cmap=plt.get_cmap('viridis'))
pc.set_array([])

with pytest.raises(ValueError, match='Unable to determine Axes to steal'):
plt.colorbar(pc)


@image_comparison(['colorbar_closed_patch.png'], remove_text=True)
def test_colorbar_closed_patch():
# Remove this line when this test image is regenerated.
Expand Down Expand Up @@ -675,7 +683,7 @@ def test_colorbar_inverted_ticks():
def test_mappable_no_alpha():
fig, ax = plt.subplots()
sm = cm.ScalarMappable(norm=mcolors.Normalize(), cmap='viridis')
fig.colorbar(sm)
fig.colorbar(sm, ax=ax)
sm.set_cmap('plasma')
plt.draw()

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