How to use unicode symbols in matplotlib?

Question

import matplotlib.pyplot as pyplot

pyplot.figure()
pyplot.xlabel(u"\u2736")
pyplot.show()

Here is the simplest code I can create to show my problem. The axis label symbol is meant to be a six-pointed star but it shows as a box. How do I change it so the star is shown? I've tried adding the comment:

#-*- coding: utf-8 -*-

like previous answers suggested but it didn't work, as well as using matplotlib.rc or matplotlib.rcParams which also didn't work. Help would be appreciated.

Answer 1

To complement @arjenve's answer. To plot a Unicode character, firstly, find which font contains this character, secondly, use that font to plot characters with Matplotlib

Find a font which contains the character

According to this post, we can use fontTools package to find which font contains the character we want to plot.

from fontTools.ttLib import TTFont
import matplotlib.font_manager as mfm

def char_in_font(unicode_char, font):
    for cmap in font['cmap'].tables:
        if cmap.isUnicode():
            if ord(unicode_char) in cmap.cmap:
                return True
    return False

uni_char =  u"?"
# or uni_char = u"\u2739"

font_info = [(f.fname, f.name) for f in mfm.fontManager.ttflist]

for i, font in enumerate(font_info):
    if char_in_font(uni_char, TTFont(font[0])):
        print(font[0], font[1])

This script will print a list of font paths and font names (all these fonts support that Unicode Character). Sample output shown below

Then, we can use the following script to plot this character (see image below)

import matplotlib.pyplot as plt
import matplotlib.font_manager as mfm

font_path = '/usr/share/fonts/gnu-free/FreeSerif.ttf'
prop = mfm.FontProperties(fname=font_path)
plt.text(0.5, 0.5, s=uni_char, fontproperties=prop, fontsize=20)

plt.show()