Python: Trying to convert string to datetime

Question

This is my code

import datetime
str = "2020-12-24 14:05:56.449122"
e = datetime.datetime.strptime(str, '%y-%m-%d %H:%M:%S.%f')
print(e)

It shows this error--

time data '2020-12-24 14:05:56.449122' does not match format '%y-%m-%d %H:%M:%S.%f