import matplotlib.pyplot as plt
plt.plot()
plt.xlabel(r'Production$_{world}$')
As shown in image red frame, the word 'World' I don't want it to be italicized.
You can do this by adding font settings.
import matplotlib.pyplot as plt
fig = plt.figure(figsize=(4,3),dpi=144)
plt.plot()
plt.xlabel(r'Production$_\mathrm{world}$')