Matplotlib 2.0.0 seems to have changed the default legend location from "upper right" to "best" (although the documentation doesn't say this). I have noticed that this results in a severe performance penalty: several plots which would normally render in a fraction of a second now need 5-10 seconds. To make things worse, the legend location is recalculated whenever the plot is moved or zoomed. The sharex/sharey functionality which I use quite a lot makes this even slower, since all subplots are moved or zoomed simultaneously.

Code for reproduction

from pylab import *

x = linspace(0, 100, 100000)

close("all")
figure("Test", figsize=(12, 8))
for j in range(9):
	if j == 0:
		ax = subplot(3, 3, 1)
	else:
		subplot(3, 3, j + 1, sharex=ax, sharey=ax)
	for i in range(8):
		plot(x, sin(x + i * 0.5), color=cm.magma(i/8), label="test")
	legend(fontsize="small")

tight_layout()
show()

Matplotlib version

• Matplotlib 2.0.0 (installed with pip)
• Python 3.6.0 (compiled from source)
• Platform: Linux (CentOS 6)