'str' object has no attribute 'strftime'

Question

I am getting this error in my script

'str' object has no attribute 'strftime'

df.set_index('Profile_ID', inplace=True)
df['CohortGroup'] = df.groupby(level=0)['Date_of_Service_Requested'].min().apply(lambda x: x.strftime('%Y-%m')) 
df.reset_index(inplace=True)
df.head()

Answer 1

strftime is a datetime method, not a str method. You can create a datetime series using pd.to_datetime:

import pandas as pd
df = pd.DataFrame({'date_column': ['2019-03-15', '2016-12-05'],
                   'other_column': [10, 4]})
df['date_column'] = pd.to_datetime(arg=df['date_column'], 
                                   format='%Y-%m-%d')
df['date_column'].apply(lambda x: x.strftime('%Y-%m'))