python - Replace whole string if it contains substring in pandas

Question

I want to replace all strings that contain a specific substring. So for example if I have this dataframe:

import pandas as pd
df = pd.DataFrame({'name': ['Bob', 'Jane', 'Alice'], 
                   'sport': ['tennis', 'football', 'basketball']})

I could replace football with the string 'ball sport' like this:

df.replace({'sport': {'football': 'ball sport'}})

What I want though is to replace everything that contains ball (in this case football and basketball) with 'ball sport'. Something like this:

df.replace({'sport': {'[strings that contain ball]': 'ball sport'}})

Answer 1

You can use str.contains to mask the rows that contain 'ball' and then overwrite with the new value:

In [71]:
df.loc[df['sport'].str.contains('ball'), 'sport'] = 'ball sport'
df

Out[71]:
    name       sport
0    Bob      tennis
1   Jane  ball sport
2  Alice  ball sport

To make it case-insensitive pass `case=False:

df.loc[df['sport'].str.contains('ball', case=False), 'sport'] = 'ball sport'