Why can't I subclass datetime.date?

Question

Why doesn\'t the following work (Python 2.5.2)?

>>> import datetime
>>> class D(datetime.date):
        def __init__(self, year):
                  


        

Answer 1

Regarding several other answers, this doesn't have anything to do with dates being implemented in C per se. The __init__ method does nothing because they are immutable objects, therefore the constructor (__new__) should do all the work. You would see the same behavior subclassing int, str, etc.

>>> import datetime
>>> class D(datetime.date):
        def __new__(cls, year):
            return datetime.date.__new__(cls, year, 1, 1)


>>> D(2008)
D(2008, 1, 1)