How to write uppercase bold italic letters matplotlib using LaTeX?

Question

I want to have the text shown in the image 1 in a plot (this is taken from Rubidium 87 D Line Data - Daniel A. Steck, page 23). It's a simple equation involving an uppercase letter, in bold italics, with font Computer Modern . So far I've tried

import matplotlib.pyplot as plt
plt.rcParams["text.usetex"] = True
plt.rcParams["text.latex.preamble"].join([
    r"\usepackage{bm}",
    r"\usepackage{amsmath}"])


fig, ax = plt.subplots()

# Not bold
ax.text(0, 0.5, r"$F=0$", fontsize=18)

# Not italic
ax.text(0.2, 0.5, r"$\mathbf{F=0}$", fontsize=18)

# Not italic, not the correct font
ax.text(0.4, 0.5, r"\textit{\textbf{F}}=0", fontsize=18)

# Returns an error from LaTeX
ax.text(0.6, 0.5, r"$\bm{F}=0$", fontsize=18)

# Returns an error from LaTeX
ax.text(0.8, 0.5, r"$\boldsymbol{F}=0$", fontsize=18)

I'm using pdfTeX, Version 3.141592653-2.6-1.40.23 (TeX Live 2021/W32TeX) to display the equations.

Answer 1

It doesn't seem like you want to achieve anything TeX specific, so you can slip away with doing it all by tweaking your rcParams and the rest when calling plt.text

>>> plt.rc('font', **{'family': 'serif', 'serif': ['Computer Modern']})
>>> plt.text(0,0,text.upper(), fontweight='bold', fontstyle='italic')

Answer 2

I found a way to make it run. For some reason the preamble was not set properly. The following code did the job:

import matplotlib.pyplot as plt
plt.rcParams["text.usetex"] = True
plt.rcParams["text.latex.preamble"] = r"\usepackage{bm}"

fig, ax = plt.subplots()
ax.text(0.6, 0.5, r"$\bm{F}\:\mathbf{=0}$", fontsize=18)