You are reading documentation for the unreleased version of Matplotlib. Try searching for the released version of this page instead?
Version 2.1.1.post1088+gf4bcca3
matplotlib
Fork me on GitHub

This Page

matplotlib.axes.Axes.format_ydata

Axes.format_ydata(y)

Return y string formatted. This function will use the fmt_ydata attribute if it is callable, else will fall back on the yaxis major formatter