Assign specific colours to data in Matplotlib pie chart

Question

I\'m trying to create pie charts with matplotlib in which the colour of each category is fixed.

I\'ve got a function which creates a pie chart from sets

Answer 1

Here is a simpler solution to @tmdavison's answer.

Let's first see the problem with an MWE:

import matplotlib.pyplot as plt

labels = ['Frogs', 'Hogs', 'Dogs', 'Logs']
sizes = [15, 30, 45, 10]

fig, ax = plt.subplots(1, 2)

ax[0].pie(sizes, labels=labels)
ax[1].pie(sizes[1:], labels=labels[1:])

This produces the problem plots:

The problem is that in the left-hand plot, Hogs is coloured in orange, but in the right-hand plot Hogs is coloured in blue (with a similar mix-up for Logs and Dogs).

We would like the colours for the labels to be the same across both plots. We can do this by specifying a dictionary of colours to use:

labels = ['Frogs', 'Hogs', 'Dogs', 'Logs']
sizes = [15, 30, 45, 10]
colours = {'Frogs': 'C0',
           'Hogs': 'C1',
           'Dogs': 'C2',
           'Logs': 'C3'}

fig, ax = plt.subplots(1, 2)

ax[0].pie(sizes,
          labels=labels,
          colors=[colours[key] for key in labels])

ax[1].pie(sizes[1:],
          labels=labels[1:],
          colors=[colours[key] for key in labels[1:]])

This works to create the plot:

Here we see that the labels are represented by the same colours across both plots, as desired.

If you have lots of categories it can be cumbersome to manually set a colour for each category. In this case you could construct the colours dictionary as:

colours = dict(zip(labels, plt.cm.tab10.colors[:len(labels)]))

If you have more than 10 categories you would instead use:

colours = dict(zip(labels, plt.cm.tab20.colors[:len(labels)]))