>>> import pandas as pd
>>> df = pd.DataFrame([[1, 'aaaa'], [3, 'aabcz'], [4, 'abcd']], columns='n s'.split(' '), index=[10, 20, 30])
>>> df
n s
10 1 aaaa
20 3 aabcz
30 4 abcd
>>> df['n'][df['s'].map(lambda x: 'abc' in x)] = 9
>>> df
n s
10 1 aaaa
20 9 aabcz
30 9 abcd