how to compare two columns in pandas to make a third column ?

Question

i have two columns age and sex in a pandas dataframe

sex = [\'m\', \'f\' , \'m\', \'f\', \'f\', \'f\', \'f\']
age = [16 ,  15 , 14 , 9  , 8   , 2   , 56 ]
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Answer 1

df = pd.DataFrame({'sex':['m', 'f' , 'm', 'f', 'f', 'f', 'f'],
    'age':[16, 15, 14, 9, 8, 2, 56]})
df['yes'] = df.apply(lambda x: 'child' if x['age'] <= 9 else x['sex'], axis=1)

Result:

   age sex    yes
0   16   m      m
1   15   f      f
2   14   m      m
3    9   f  child
4    8   f  child
5    2   f  child
6   56   f      f