BUG: Groupby.transform('size') fails for multicolumn frame · Issue #27469 · pandas-dev/pandas (original) (raw)

from pandas import * df = DataFrame(dict(a=[0, 0, 0, 1, 1, 1], b=range(6))) g = df.groupby(np.repeat([0,1], 3))

ok

print(g.size()) #fails g.transform('size') TypeError: Transform function invalid for data types