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' 

Answer 2

You can use apply with a lambda. The x parameter of the lambda function will be each value in the 'sport' column:

df.sport = df.sport.apply(lambda x: 'ball sport' if 'ball' in x else x)