Binning Numbers

An airline charges a bag by its weight class, not by the gram. Binning turns numbers into ranges, called bins, for when only the range matters:

pd.cut takes the values, the edges and one label per bin:

bags = pd.DataFrame({"kg": [5.5, 23.0, 18.2, 30.5, 7.0, 12.4]})
bags["class"] = pd.cut(bags["kg"], bins=[0, 7, 23, 32],
                       labels=["cabin", "standard", "heavy"])
print(bags["class"].value_counts().sort_index())

This prints:

class
cabin       2
standard    3
heavy       1
Name: count, dtype: int64

Each bin includes its right edge, so 7.0 kg is still cabin, and a value outside the edges becomes NaN.

.sort_index() lists the bins in their own order, lightest first.