PR Summary

constrained_layout adds a unique number to each layout element. However, if many figures are open
this number was overflowing 1000. For some reason kiwisolver doesn't like the longer integers in the variable names (which is a bit of a mystery in itself, but kind of moot - if someone had 1000 elements in their constrained_layout I think they'd be pretty sad about how long it took to render).

This simply resets the iterator every time a new figure is made....

No test, as it requires making > 1000 elements, and it'd take quite a while (~60 s or so on my machine, though I'm doing a write as well). Also not sure how to check that the last CL is correct.

Test code:

import numpy as np
import matplotlib.pyplot as plt

plt.ioff()
fig = None
for a in range(40):
    fig, ax = plt.subplots(4, 4, constrained_layout=True)
    ax = ax.flatten()
    ax[0].plot(range(10))
    ax[1].plot(range(20))
    fig.savefig('booos/boo%03d.png'%a)

PR Checklist

• Code is PEP 8 compliant