How to change legend patches after plotting?

I have a function that is supposed to enlarge all labels in a figure to make it ready for export. However I fail to enlarge the legend properly:

import matplotlib.pyplot as plt

def enlarge_legend(ax, fontSize = 25):
    for text in ax.get_legend().get_texts():
        text.set_fontsize(fontSize)


fig, ax = plt.subplots()
ax.scatter(
        [1,2,3],
        [2,3,1],
        label = "auto"
        )
ax.legend()
enlarge_legend(ax)

result:

I would like the circle patch to be bigger as well but both ax.get_legend().get_patches() and ax.get_legend().get_lines() return empty lists. Any idea how to do it?

The dot in your legend is a PathCollection, so you have to tweak either markerscale when you create the legend, or the handle sizes after the legend exists.

fig, ax = plt.subplots()
ax.scatter([1, 2, 3], [2, 3, 1], label='auto')

# option A – easiest: change legend as you make it
ax.legend(fontsize=25, markerscale=3)          # ← “3” makes the dot ≈3× larger

or, with your current enlarge_legend helper:

def enlarge_legend(ax, size=25, marker_area=200):
    lgd = ax.get_legend()
    for txt in lgd.get_texts():          # enlarge text
        txt.set_fontsize(size)
    for h in lgd.legendHandles:          # enlarge scatter marker
        h.set_sizes([marker_area])       # area in points²

fig, ax = plt.subplots()
ax.scatter([1, 2, 3], [2, 3, 1], label='auto')
ax.legend()
enlarge_legend(ax)

Either way the marker in the legend will grow to match (or exceed) the symbol size you see in the plot.