# Based on test_combine_datetlike_udf df = pd.DataFrame({"A": range(5), "B": range(5)}) df.columns = ["A", "A"] other = df.copy() df.iloc[1, :] = None def combiner(a, b): return b >>> df.combine(other, combiner) AttributeError: 'DataFrame' object has no attribute 'dtype'. Did you mean: 'dtypes'?