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BUG: matplotlib 3.4.0 -- Scatter with colormap and legend gives TypeError: object of type 'NoneType' has no len() #19779
Description
Bug report
Bug summary
With matplotlib 3.4.0, scatter plot with colormap and legend gives TypeError: object of type 'NoneType' has no len().
Code for reproduction
import matplotlib.pyplot as plt
y = [1, 2, 3, 4, 5]
plt.scatter(y, y, label='Y', lw=0, s=8, c=y, cmap='viridis')
plt.legend()
plt.show()Actual outcome
Traceback (most recent call last):
File ".../matplotlib/backends/backend_qt5.py", line 475, in _draw_idle
self.draw()
File ".../matplotlib/backends/backend_agg.py", line 406, in draw
self.figure.draw(self.renderer)
File ".../matplotlib/artist.py", line 74, in draw_wrapper
result = draw(artist, renderer, *args, **kwargs)
File ".../matplotlib/artist.py", line 51, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)
File ".../matplotlib/figure.py", line 2734, in draw
mimage._draw_list_compositing_images(
File ".../matplotlib/image.py", line 132, in _draw_list_compositing_images
a.draw(renderer)
File ".../matplotlib/artist.py", line 51, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)
File ".../matplotlib/_api/deprecation.py", line 431, in wrapper
return func(*inner_args, **inner_kwargs)
File ".../matplotlib/axes/_base.py", line 2925, in draw
mimage._draw_list_compositing_images(renderer, self, artists)
File ".../matplotlib/image.py", line 132, in _draw_list_compositing_images
a.draw(renderer)
File ".../matplotlib/artist.py", line 51, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)
File ".../matplotlib/legend.py", line 614, in draw
self._legend_box.draw(renderer)
File ".../matplotlib/offsetbox.py", line 368, in draw
c.draw(renderer)
File ".../matplotlib/offsetbox.py", line 368, in draw
c.draw(renderer)
File ".../matplotlib/offsetbox.py", line 368, in draw
c.draw(renderer)
[Previous line repeated 1 more time]
File ".../matplotlib/offsetbox.py", line 694, in draw
c.draw(renderer)
File ".../matplotlib/artist.py", line 51, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)
File ".../matplotlib/collections.py", line 1009, in draw
super().draw(renderer)
File ".../matplotlib/artist.py", line 51, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)
File ".../matplotlib/collections.py", line 380, in draw
len(facecolors) == 1 and len(edgecolors) == 1 and
TypeError: object of type 'NoneType' has no len()
Expected outcome
With matplotlib 3.3.4, I get this (no warning or error):
Matplotlib version
- Operating system: Red Hat Enterprise Linux Server release 7.9 (Maipo)
- Matplotlib version (
import matplotlib; print(matplotlib.__version__)): 3.4.0 - Matplotlib backend (
print(matplotlib.get_backend())): Qt5Agg - Python version: 3.8.3
- Jupyter version (if applicable): N/A
- Other libraries: Not sure what else you need, just let me know.
Activity
smartlixx commentedon Mar 27, 2021
A bisect diagnose shows that the problem was introduced in the commit
4c3d644 (#18480), which changed the way Collections deal with color.
A quick fix is easy, but I don't have much in-depth understanding of this part of the code. If anyone familiar with this part can have a discussion, that would be great. Or I just open a PR for discussion.
dstansby commentedon Mar 28, 2021
Opening a PR is probably the best way forward 👍
smartlixx commentedon Mar 29, 2021
Actually, this problem has been solved in the commit ed6d92b (#19552), but this commit was not included in v3.4.x branch. Backport that commit will solve this problem.
QuLogic commentedon Mar 29, 2021
That commit removes API and cannot be included in v3.4.x directly.
QuLogic commentedon Mar 29, 2021
Maybe we should just drop the
self._check_update('array')though, @efiring?Fix legend of colour-mapped scatter plots.
Downgrade matplotlib to bypass their bug in legend of scatter plot - m…
Copy new attributes in Collection.update_from.
QuLogic commentedon Mar 31, 2021
Closed by #19816.
pllim commentedon Mar 31, 2021
Thanks for the quick fix!