On Wed, 2007-07-25 at 19:11 +0000, Marc 'BlackJack' Rintsch wrote: > And just calling `iter()` doesn't work either: > > In [72]: class A: > ....: def __getitem__(self, key): > ....: if key == 42: > ....: return 'answer' > ....: raise KeyError > ....: > > In [73]: iter(A()) > Out[73]: <iterator object at 0xb7829b2c> > > In [74]: a = iter(A()) > > In [75]: a.next() > --------------------------------------------------------------------------- > <type 'exceptions.KeyError'> Traceback (most recent call last) > > /home/bj/<ipython console> in <module>() > > /home/bj/<ipython console> in __getitem__(self, key) > > <type 'exceptions.KeyError'>: > > > So there's no reliable way to test for "iterables" other than actually > iterate over the object.
You seem to say that your 'a' object is not iterable. I disagree. While it's true that it raises an exception upon retrieval of the zeroth iteration, that situation is quite different from attempting to iterate over the number 10, where you can't even ask for a zeroth iteration. To illustrate this point further, imagine you write an object that iterates over the lines of text read from a socket. If the connection is faulty and closes the socket before you read the first line, the zeroth iteration raises an exception. Does that mean the object is iterable or not depending on the reliability of the socket connection? I find that notion hard to swallow. -- Carsten Haese http://informixdb.sourceforge.net -- http://mail.python.org/mailman/listinfo/python-list
