python - Matplotlib how to set legend's font type

Question

I want to change the font type of the legend texts in Matplotlib. I know I can do something like this:

plt.legend(prop={'family': 'Arial'})

But I want to use a Chinese font type and I have no idea what is the family name I should put in the line above. But I do have a fontproperties object to that Chinese font type. However, I haven't found a way to set the fontproperties of the legend.

So two questions:

1. How to find the name of a particular font's family name
2. How to set fontproperties of the legend

Answer 1

Pass the FontProperties object (such as font below) to ax.legend via the prop parameter:

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.font_manager as font_manager

fig, ax = plt.subplots()
x = np.linspace(-10, 10, 100)
ax.plot(np.sin(x)/x, label='Mexican hat')

font = font_manager.FontProperties(family='Comic Sans MS',
                                   weight='bold',
                                   style='normal', size=16)
ax.legend(prop=font)
plt.show()

On Ubuntu, you can make new fonts available to your system by running

fc-cache -f -v /path/to/fonts/directory

I'm not sure how it is done on other OSes, or how universal fc-cache is on other flavors of Unix.

---

Once you've installed your font(s) so that your OS knows about them, you can cause matplotlib to regenerate its fontList by deleting the files in ~/.cache/fontconfig and ~/.cache/matplotlib.

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The ~/.cache/matplotlib/fontList.json file gives you a humanly-readable list of all the fonts matplotlib knows about. There, you'll find entries that look like this:

{
  "weight": "bold",
  "stretch": "normal",
  "fname": "/usr/share/fonts/truetype/msttcorefonts/Comic_Sans_MS_Bold.ttf",
  "_class": "FontEntry",
  "name": "Comic Sans MS",
  "style": "normal",
  "size": "scalable",
  "variant": "normal"
},

Notice that the fname is the path to the underlying ttf file, and that there is a name property as well. You can specify the FontProperties object by the path to the ttf file:

font = font_manager.FontProperties(fname="/usr/share/fonts/truetype/msttcorefonts/Comic_Sans_MS_Bold.ttf")

or by name:

font = font_manager.FontProperties(family='Comic Sans MS',
                                   weight='bold',
                                   style='normal', size=16)

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If you do not wish to install your font system-wide, you can specify the FontProperties object by fname path, thus by-passing the need to call fc-cache and messing with ~/.cache.