By far my favorite feature of matplotlib is that it produces readable and accessible plots by default. Font sizes and linewidths are not too small, the default color palette is colorblind-friendly, and the default colormaps are perceptually uniform. Other software (for example Matlab and Mathematica) have absolutely terrible defaults and require a lot of fiddling to get the plots right.
import matplotlib
theme = {'axes.grid': True,
'grid.linestyle': '--',
'legend.framealpha': 1,
'legend.facecolor': 'white',
'legend.shadow': True,
'legend.fontsize': 14,
'legend.title_fontsize': 16,
'xtick.labelsize': 14,
'ytick.labelsize': 14,
'axes.labelsize': 16,
'axes.titlesize': 20,
'figure.dpi': 100}
matplotlib.rcParams.update(theme)