[Doc]: legend guide should be OO

[story645]

Documentation Link

https://matplotlib.org/devdocs/tutorials/intermediate/legend_guide.html

Problem

The legend guide is all pyplot interface, which is especially discouraged in the types of examples (complicated, some needing state) in the guide. For example:

from matplotlib.legend_handler import HandlerPatch


class HandlerEllipse(HandlerPatch):
    def create_artists(self, legend, orig_handle,
                       xdescent, ydescent, width, height, fontsize, trans):
        center = 0.5 * width - 0.5 * xdescent, 0.5 * height - 0.5 * ydescent
        p = mpatches.Ellipse(xy=center, width=width + xdescent,
                             height=height + ydescent)
        self.update_prop(p, orig_handle, legend)
        p.set_transform(trans)
        return [p]


c = mpatches.Circle((0.5, 0.5), 0.25, facecolor="green",
                    edgecolor="red", linewidth=3)
plt.gca().add_patch(c)

plt.legend([c], ["An ellipse, not a rectangle"],
           handler_map={mpatches.Circle: HandlerEllipse()})

Suggested improvement

switch the tutorial to OO

Matplotlib Version

3.4.2.post1539+gf8f693922c

Matplotlib documentation version

3.4.2.post1539+gf8f693922c

[BhaswatiRoy]

Under legend location can we just add the "best" parameter with a sample of code with output since it is the most commonly used and most important. Also, we can add plots for some more legend locations to make things clearer. Just like the following ss->

[timhoffm]

Closed by #20792.