python - Sans-serif math with latex in matplotlib

Question

The following script:

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as mpl

mpl.rc('font', family='sans-serif')
mpl.rc('text', usetex=True)

fig = mpl.figure()
ax = fig.add_subplot(1,1,1)
ax.text(0.2,0.5,r"Math font: $451^circ$")
ax.text(0.2,0.7,r"Normal font (except for degree symbol): 451$^circ$")

fig.savefig('test.png')

is an attempt to use a sans-serif font in matplotlib with LaTeX. The issue is that the math font is still a serif font (as indicated by the axis numbers, and as demonstrated by the labels in the center). Is there a way to set the math font to also be sans-serif?

Answer 1

I always have text.usetex = True in my matplotlibrc file. In addition to that, I use this as well:

mpl.rcParams['text.latex.preamble'] = [
       r'usepackage{siunitx}',   # i need upright micro symbols, but you need...
       r'sisetup{detect-all}',   # ...this to force siunitx to actually use your fonts
       r'usepackage{helvet}',    # set the normal font here
       r'usepackage{sansmath}',  # load up the sansmath so that math -> helvet
       r'sansmath'               # <- tricky! -- gotta actually tell tex to use!
]  

Hope that helps.