#if you have a column whose format is datetime in your dataframe,
#and you want to extract the month name from it in a list
df['datetime_column'].dt.month_name()
#returns list of full month names (e.g. January, February)
df['Month'] = pd.to_datetime(df['Month'], format='%m').dt.month_name().str.slice(stop=3)
df
Month client
0 Feb sss
1 Dec yyy
2 Jun www