BUG: groupby mean/median/var should always be float values · Issue #41137 · pandas-dev/pandas (original) (raw)

This is value-dependent behavior:

print(DataFrame({'a': [1, 3]}).groupby([1, 1]).mean())

results in the integer 2, whereas

print(DataFrame({'a': [1, 3]}).mean())

results in 2.0.