Hi,
If I implement __len__ in my own class, does it really have to return an int?
Is there no way around this (other than modifying the source code of python
itself ;-) It would be nice if len(Example(row, col)) would return a
dictionary, or a two-tuple (see code below). The strange thing is that calling
__len__ directly does work: Example(1, 2).__len__() returns the dictionary. I
always thought len() was a convenient "shorthand" for __len__. I've even been
reading about metaclasses (interesting, dark, mysterious), thinking the answer
might lie there. Note that my question is not whether it's a good idea to do
this, I just find it interesting to understand how it could be done.
Python 2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit (Intel)] on
win32
>>> class Example(object):
def __init__(self, row, col):
self.row = row
self.col = col
def __len__(self):
return {self.row: self.col}
>>> len(Example(1, 2))
Traceback (most recent call last):
File "<pyshell#29>", line 1, in <module>
len(Example(1, 2))
TypeError: an integer is required
>>> Example(1, 2).__len__()
{1: 2}
Regards,
Albert-Jan
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