python - How to set font size of Matplotlib axis Legend?

Question

I have a code like this:

import matplotlib.pyplot as plt
from matplotlib.pyplot import *
from matplotlib.font_manager import FontProperties

fontP = FontProperties()
fontP.set_size('xx-small')
fig=plt.figure()
ax1=fig.add_subplot(111)
plot([1,2,3], label="test1")
ax1.legend(loc=0, ncol=1, bbox_to_anchor=(0, 0, 1, 1),
           prop = fontP,fancybox=True,shadow=False,title='LEGEND')
plt.show()

It can be seen in the plot that the setting in Fontsize does not affect the Legend Title font size.

How to set the font size of the legend title to a smaller size?

Answer 1

This is definitely an old question, but was frustrating me too and none of the other answers changed the legend title fontsize at all, but instead just changed the rest of the text. So after banging my head against the matplotlib documentation for awhile I came up with this.

legend = ax1.legend(loc=0, ncol=1, bbox_to_anchor=(0, 0, 1, 1),
           prop = fontP,fancybox=True,shadow=False,title='LEGEND')

plt.setp(legend.get_title(),fontsize='xx-small')

As of Matplotlib 3.0.3, you can also set it globally with

plt.rcParams['legend.title_fontsize'] = 'xx-small'

Answer 2

Here is how to change the fontsize of the legend list and/or legend title:

legend=plt.legend(list,loc=(1.05,0.05), title=r'$\bf{Title}$') #Legend: list, location, Title (in bold)
legend.get_title().set_fontsize('6') #legend 'Title' fontsize
plt.setp(plt.gca().get_legend().get_texts(), fontsize='12') #legend 'list' fontsize

Answer 3

Banged my head against it too, here is another more flowing way of doing it:

leg = ax.legend()
leg.set_title('A great legend',prop={'size':14})

Answer 4

I don't know how to set it up for an individual plot, but I always do it globally:

plt.rc('legend',**{'fontsize':6})

Answer 5

Inspired by the current top answer, I found a slightly more natural way to change the fontsizes in the legend. The fontsize argument sets the font size of each of the data labels, and the title_fontsize argument sets the fontsize of the title, if you give the legend a title.

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.plot([0,1,2],[2,1,2],label='test_data (fs=12)')
ax.legend(fontsize=12, title='TITLE (fs=30)',title_fontsize=30)

Gives a figure like this:

Answer 6

This is the fastest:

plt.legend(loc=2,prop={'size':6})

Answer 7

I generally do in this way. Once the plot has been done i do the following

plt.legend(loc=0, numpoints=1)
leg = plt.gca().get_legend()
ltext  = leg.get_texts()
plt.setp(ltext, fontsize='small') 

I don't know if this works for you

Answer 8

Now in 2021, with matplotlib 3.4.2 you can set your legend fonts with

plt.legend(title="My Title", fontsize=10, title_fontsize=15)

where fontsize is the font size of the items in legend and title_fontsize is the font size of the legend title. More information in matplotlib documentation