Bug report

Bug summary

The SymPy 1.5 documentation was built with matpltolib < 3.2, see the results here:

https://docs.sympy.org/latest/modules/plotting.html

Example image:

The SymPy development documentation (SymPy master branch) is now built with matplotlib 3.2, see the results here:

https://docs.sympy.org/dev/modules/plotting.html

Example image:

I've been documenting the issue over at SymPy here: sympy/sympy#19051

Code for reproduction

Note that SymPy has a wrapper around various plotting libraries and it will run matplotlib as the backend by default. I have not yet isolated what underlying mpl code in the SymPy wrapper is specifically affected.

from sympy import symbols
from sympy.plotting import plot
x = symbols('x')
p1 = plot(x*x, show=False)
p2 = plot(x, show=False)
p1.append(p2[0])
p1.show()

Actual outcome

# If applicable, paste the console output here
#
#

Expected outcome

Matplotlib version

• Operating system: Ubuntu 18.04 and 19.10
• Matplotlib version: 3.1 and 3.2
• Matplotlib backend (print(matplotlib.get_backend())):
• Python version: 3.6-3.8
• Jupyter version (if applicable):
• Other libraries: SymPy 1.5

Checked with MPL from conda-forge.