Lambda Function

import pandas as pd
content = ['hi','hello','how are you']
df=pd.DataFrame(content,columns={'Sms content'})
df
Sms content
0 hi
1 hello
2 how are you 
df['msg_length'] = df['Sms content'].apply(lambda x:len(x))
df.head()
Sms content msg_length
0 hi 2
1 hello 5
2 how are you 11