Jupyter Assertion Error / AttributeError: can't set attribute 'renderer'

[timbmg]

I am following Brienna's Gist to plot emojis in matplotlib, which has the following code:

# Set the backend to use mplcairo 
import matplotlib, mplcairo
print('Default backend: ' + matplotlib.get_backend()) 
matplotlib.use("module://mplcairo.macosx")
print('Backend is now ' + matplotlib.get_backend())

# IMPORTANT: Import these libraries only AFTER setting the backend
import matplotlib.pyplot as plt, numpy as np
from matplotlib.font_manager import FontProperties

# Load Apple Color Emoji font 
prop = FontProperties(fname='/System/Library/Fonts/Apple Color Emoji.ttc')

# Set up plot
freqs = [301, 96, 53, 81, 42]
labels = ['😊', '😱', '😂', '😄', '😛']
plt.figure(figsize=(12,8))
p1 = plt.bar(np.arange(len(labels)), freqs, 0.8, color="lightblue")
plt.ylim(0, plt.ylim()[1]+30)

# Make labels
for rect1, label in zip(p1, labels):
    height = rect1.get_height()
    plt.annotate(
        label,
        (rect1.get_x() + rect1.get_width()/2, height+5),
        ha="center",
        va="bottom",
        fontsize=30,
        fontproperties=prop
    )

plt.show()

When running this in jupyter notebook, i get the following error: python[13573:53170] *** Assertion failure in +[NSEvent otherEventWithType:location:modifierFlags:timestamp:windowNumber:context:subtype:data1:data2:], NSEvent.m:647

When running this in a python script I get:

Default backend: MacOSX
Backend is now module://mplcairo.macosx
Traceback (most recent call last):
  File "/opt/homebrew/Caskroom/miniconda/base/envs/proj/lib/python3.10/site-packages/matplotlib/backend_bases.py", line 1226, in _on_timer
    ret = func(*args, **kwargs)
  File "/opt/homebrew/Caskroom/miniconda/base/envs/proj/lib/python3.10/site-packages/matplotlib/backends/backend_macosx.py", line 68, in callback_func
    callback()
  File "/opt/homebrew/Caskroom/miniconda/base/envs/proj/lib/python3.10/site-packages/matplotlib/backends/backend_macosx.py", line 88, in _draw_idle
    self.draw()
  File "/opt/homebrew/Caskroom/miniconda/base/envs/proj/lib/python3.10/site-packages/mplcairo/base.py", line 233, in draw
    super().draw()
  File "/opt/homebrew/Caskroom/miniconda/base/envs/proj/lib/python3.10/site-packages/matplotlib/backends/backend_macosx.py", line 50, in draw
    super().draw()
  File "/opt/homebrew/Caskroom/miniconda/base/envs/proj/lib/python3.10/site-packages/matplotlib/backends/backend_agg.py", line 394, in draw
    self.renderer = self.get_renderer()
AttributeError: can't set attribute 'renderer'

I am on a Mac (M2) and mplcairo.get_versions() gives: { 'python': '3.10.8 (main, Nov 24 2022, 08:08:27) [Clang 14.0.6 ]', 'mplcairo': '0.5', 'matplotlib': '3.7.2', 'cairo': '1.16.0', 'freetype': '2.12.1', 'pybind11': '2.11.1', 'raqm': None, 'hb': None }

[anntzer]

Can you try at least the python script with matplotlib 3.8 (which has just been released)? I do see that there's an issue with 3.7.2, though I haven't investigated the cause yet.

For the notebook integration, I think this needs to be reported to matplotlib itself, as even a simple

import matplotlib as mpl; mpl.use("macosx")
from matplotlib import pyplot as plt
plt.plot()

(i.e. using matplotlib's own macosx backend, which mplcairo still relies on) in a notebook seems to crash with the same error you report. On the other hand you don't really need to use module://mplcairo.macosx; module://mplcairo.tk or module://mplcairo.qt (if you have pyqt6 installed) should work just fine.

[timbmg]

Thanks for your swift reply!

Just tried with matplotlib 3.8 and it seems to be the same issue, both as script and in the notebook.

[anntzer]

Ah yes, I remember the problem now. For the macosx backend you'll need to install mplcairo from HEAD (pip install git+https://github.com/matplotlib/mplcairo); alternatively, as noted above, you can use one of the other backends such as module://mplcairo.qt or module://mplcairo.tk.