Bug summary

We can now use a (x,y) argument for plt.legend(loc=(x,y)),
but using the tuple as a value for rcParams['legend.loc'] fails.

Code for reproduction

import matplotlib.pyplot as plt
import matplotlib as mpl
xs, ys = [1,2,3], [2,3,1]

fig, ax = plt.subplots(3)

ax[0].scatter(xs, ys, label='loc-tuple-arg')
ax[0].legend(loc=(1.1, .5)) # works

ax[1].scatter(xs, ys, label='loc-rcparam-tuple')
mpl.rcParams['legend.loc'] = (0.9, .7)
ax[1].legend() # fails w/o documentation

ax[2].scatter(xs, ys, label='loc-rcparam-str(tuple)')
mpl.rcParams['legend.loc'] = '(.8, .3)'
ax[2].legend() # fails with documentation

Actual outcome

Setting rcParams['legend.loc'] to a tuple fails with

AttributeError: 'tuple' object has no attribute 'lower'

setting rcParams['legend.loc'] to the string representation of a tuple fails with a list of supported values.

Expected outcome

Ideally rcParams['legend.loc'] would apply a tuple the same way the kwarg does.

Second best would be a bit more documentation; 1) reporting the list of supported strings for any un-interpretable value, and 2) mentioning in the default matplotlibrc that only a set of strings are supported.

Additional information

I believe the loc kwarg originally only took string values, but that seems to have been at least a major version ago.

Operating system

Ubuntu

Matplotlib Version

3.3.4

Matplotlib Backend

TkAgg

Python version

Python 3.9.7

Jupyter version

No response

Installation

pip