Just use \mathregular{whatever}in your expression.
For example:
import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.text(0.2, 0.7, 'No mathtex')
ax.text(0.2, 0.5, 'This superscript $is^{in}$ italics')
ax.text(0.2, 0.3, 'While this $\mathregular{is^{really}}$ the same font')
plt.show()

See http://matplotlib.org/users/mathtext.html for more details .
source
share