Adding Comma to Bar Labels in MatplotLib

Question

I have been using the ax.bar_label method to add data values to the bar graphs. The numbers are huge such as 143858918. How can I add commas to the data values using the ax.bar_label method? I do know how to add commas using the annotate method but if it is possible using bar_label, I am not sure. Is it possible using the fmt keyword argument that is available?

Answer 1

Is it possible using the fmt keyword argument?

• The fmt param is based on the old % operator, which doesn't support comma separators.
• Instead, use the labels param with an f-string.

Format the container's datavalues with {:,.0f} to get comma separators (increase 0 if you want more decimal places):

container = ax.containers[0]
ax.bar_label(container, labels=[f'{x:,.0f}' for x in container.datavalues])

Or for grouped bar charts, iterate all the containers:

for container in ax.containers:
    ax.bar_label(container, labels=[f'{x:,.0f}' for x in container.datavalues])

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Toy example:

x = np.random.default_rng(123).integers(10_000_000, size=5)
fig, ax = plt.subplots()
ax.bar(range(len(x)), x)

container = ax.containers[0]
ax.bar_label(container, labels=[f'{x:,.0f}' for x in container.datavalues])