from datetime import datetime

s = 'Hello, Pythoneers'
print(s == eval(repr(s)))  # no errors here

today = datetime.now()
print(today == eval(repr(today))) # error occurs here

>>> import datetime
>>> datetime.datetime.now()
datetime.datetime(2018, 5, 27, 16, 46, 59, 491342)

>>> datetime
<module 'datetime' from '/.../lib/python3.6/datetime.py'>
>>> datetime.datetime
<class 'datetime.datetime'>