Adding Comma to Bar Labels

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 of ax.bar_label?

Yes, but only in matplotlib 3.7+. Prior to 3.7, fmt only accepted % formatters (no comma support), so labels was needed to f-format the container's datavalues.

• If matplotlib ≥ 3.7, use fmt:

  for c in ax.containers:
      ax.bar_label(c, fmt='{:,.0f}')  # ≥ 3.7
      #                   ^no f here (not an actual f-string)
  

• If matplotlib < 3.7, use labels:

  for c in ax.containers:
      ax.bar_label(c, labels=[f'{x:,.0f}' for x in c.datavalues])  # < 3.7
  

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Toy example:

fig, ax = plt.subplots()
ax.bar(['foo', 'bar', 'baz'], [3200, 9025, 800])

# ≥ v3.7
for c in ax.containers:
    ax.bar_label(c, fmt='{:,.0f}')

# < v3.7
for c in ax.containers:
    ax.bar_label(c, labels=[f'{x:,.0f}' for x in c.datavalues])