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Description
Bug summary
When using subfigures, calling fig.legend() (on the main/root figure) after having drawn a stackplot (ax.stackplot) results in the following error:
RuntimeError: Can not put single artist in more than one figure
Code for reproduction
I copied the code from the stackplot example from the docs, then repeated it in a loop:
import matplotlib.pyplot as plt
import numpy as np
import matplotlib.ticker as mticker
year = [1950, 1960, 1970, 1980, 1990, 2000, 2010, 2018]
population_by_continent = {
"Africa": [0.228, 0.284, 0.365, 0.477, 0.631, 0.814, 1.044, 1.275],
"the Americas": [0.340, 0.425, 0.519, 0.619, 0.727, 0.840, 0.943, 1.006],
"Asia": [1.394, 1.686, 2.120, 2.625, 3.202, 3.714, 4.169, 4.560],
"Europe": [0.220, 0.253, 0.276, 0.295, 0.310, 0.303, 0.294, 0.293],
"Oceania": [0.012, 0.015, 0.019, 0.022, 0.026, 0.031, 0.036, 0.039],
}
fig = plt.figure()
subfigs = fig.subfigures(nrows=1, ncols=2)
for _fig in subfigs:
axs = _fig.subplots(nrows=2, ncols=1, squeeze=False)[0]
for ax in axs:
ax.stackplot(
year,
population_by_continent.values(),
labels=population_by_continent.keys(),
alpha=0.8,
)
ax.legend(loc="upper left", reverse=True)
ax.set_title("World population")
ax.set_xlabel("Year")
ax.set_ylabel("Number of people (billions)")
# add tick at every 200 million people
ax.yaxis.set_minor_locator(mticker.MultipleLocator(0.2))
fig.legend(loc="upper right", bbox_to_anchor=(1.1, 1)) # error!Actual outcome
An exception is raised
Expected outcome
A legend is drawn. If in the provided example ax.stackplot is replaced by another plotting function (i.e. ax.plot, ax.scatter...) the error does not happen.
I have also tried:
fig.legend(handles, labels): Passing a list of artist/labels to.legend()causes the same errorsubfigures[0].legend(): works, but obviously only prints artists present in said subfigure, not others.
Additional information
No response
Operating system
No response
Matplotlib Version
3.10.0
Matplotlib Backend
No response
Python version
No response
Jupyter version
No response
Installation
None