pandas.core.groupby.DataFrameGroupBy.cumcount — pandas 2.2.3 documentation (original) (raw)

DataFrameGroupBy.cumcount(ascending=True)[source]#

Number each item in each group from 0 to the length of that group - 1.

Essentially this is equivalent to

self.apply(lambda x: pd.Series(np.arange(len(x)), x.index))

Parameters:

ascendingbool, default True

If False, number in reverse, from length of group - 1 to 0.

Returns:

Series

Sequence number of each element within each group.

See also

ngroup

Number the groups themselves.

Examples

df = pd.DataFrame([['a'], ['a'], ['a'], ['b'], ['b'], ['a']], ... columns=['A']) df A 0 a 1 a 2 a 3 b 4 b 5 a df.groupby('A').cumcount() 0 0 1 1 2 2 3 0 4 1 5 3 dtype: int64 df.groupby('A').cumcount(ascending=False) 0 3 1 2 2 1 3 1 4 0 5 0 dtype: int64