understanding operator overloading

[Josh Benner]

Is there a good way to trace what's going on under the hood wrt operator
overloading?

I am trying to understand what is happening in the code and output listed
below.

Why doesn't __getitem__ in mylist return the same result as the builtin
list object?
Does it have something to do with the start and stop arguments to slice?
Is the slice object making the call to __len__?



____code___________________________________________________

class mylist():
    def __init__(self, data):
        self.data = data
    def __len__(self):
        print('len(self.data) -> self.data = {0}'.format(self.data))
        return len(self.data)
    def __getitem__(self, index):
        print('__getitem__(index) -> index = {0}'.format(index))
        return self.data[index]

if __name__ == "__main__":
    alist = [1, 2, 4]
    blist = mylist(alist)
    print('printing alist[-4:]')
    print(alist[-4:])
    print('printing blist[-4:]')
    print(blist[-4:])
    print('printing blist[-2]')
    print(blist[-2])


____output_________________________________________________

printing alist[-4:]
[1, 2, 4]
printing blist[-4:]
len(self.data) -> self.data = [1, 2, 4]
__getitem__(index) -> index = slice(-1, 9223372036854775807, None)
[4]
printing blist[-2]
__getitem__(index) -> index = -2
2


Best,
Josh Benner
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-list/attachments/20120601/3be41b68/attachment.html>