I am trying to use the case_when of a pandas Series and I am not sure I understand why it behaves like below. I indicate the behaviour that looks odd to me. It seems it has to do with the index of the Series, but why? import pandas as pd print(pd.__version__) # 2.3.0 a = pd.Series([1, 2, 3, 4, 5], index=['a', 'b', 'c', 'd', 'e'], dtype='int') b = pd.Series([1, 2, 3, 4, 5], index=['A', 'B', 'C', 'D', 'E'], dtype='int') res = a.case_when( [(a.gt(3), 'greater than 3'), (a.lt(3), 'less than 3')]) print(res) # a less than 3 # b less than 3 # c 3 # d greater than 3 # e greater than 3 res = a.case_when( [(a.gt(3), 'greater than 3'), (b.lt(3), 'less than 3')]) print(res) # a less than 3 # b less than 3 # c less than 3 <- why is this not 3? # d greater than 3 # e greater than 3 res = a.case_when( [(b.gt(3), 'greater than 3'), (b.lt(3), 'less than 3')]) print(res) # a greater than 3 <- why is this not less than 3? # b greater than 3 <- why is this not less than 3? # c greater than 3 <- why is this not 3? # d greater than 3 # e greater than 3 res = a.case_when( [(b.gt(3).to_list(), 'greater than 3'), (b.lt(3).to_list(), 'less than 3')]) print(res) # a less than 3 # b less than 3 # c 3 # d greater than 3 # e greater than 3 Continue reading...
