python - Bold font weight for LaTeX axes label in matplotlib

Question

In matplotlib you can make the text of an axis label bold by

plt.xlabel('foo',fontweight='bold')

You can also use LaTeX with the right backend

plt.xlabel(r'$phi$')

When you combine them however, the math text is not bold anymore

plt.xlabel(r'$phi$',fontweight='bold')

Nor do the following LaTeX commands seem to have any effect

plt.xlabel(r'$f phi$')
plt.xlabel(r'$mathbf{phi}$')

How can I make a bold $phi$ in my axis label?

Answer 1

Unfortunately you can't bold symbols using the bold font, see this question on tex.stackexchange.

As the answer suggests, you could use oldsymbol to bold phi:

r'$oldsymbol{phi}$'

You'll need to load amsmath into the TeX preamble:

matplotlib.rc('text', usetex=True)
matplotlib.rcParams['text.latex.preamble']=[r"usepackage{amsmath}"]