Why can't I subclass datetime.date?
datetime, oop, python, subclass
Solution
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)
Problem
Why doesn't the following work (Python 2.5.2)? ``` >>> import datetime >>> class D(datetime.date): def __init__(self, year): datetime.date.__init__(self, year, 1, 1) >>> D(2008) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: function takes exactly 3 arguments (1 given) ``` I wanted to create a class that was just like `datetime.date`, but with a different `__init__` function. Apparently my function never gets called. Instead the original `datetime.date.__init__` is called and fails because that expects 3 arguments and I am passing in one. What's going on here? And is this a clue? ``` >>> datetime.date.__init__ <slot wrapper '__init__' of 'object' objects> ``` Thanks!