spike wrote: > I've googled like crazy and can't seem to find an answer to why this > isn't working. > > I want to create a custom list class that acts as a circular list. > > ie: my_list = (0, 1, 2) > > how I want it to behave: > > my_list[0] -> 0 > my_list[1] -> 1 > my_list[2] -> 2 > my_list[3] -> 0 > my_list[4] -> 1 > ...etc > > so, what I've tried to do is: > > def circular_list(list): > def __getitem__(self, i): > if (i >= len(self)): > return self[i % len(self)] > else: > return self[i] > > items = circular_list(range(8)) > > however, when I want to iterate over it with a for statement, I get: > > TypeError: iteration over non-sequence
You also need to post the code that raises the error, or no one else can debug it. > what am I missing? I have no idea why you get that error. I do not in Python 2.4.1. However, I also don't get what you desire either. Iteration over lists (and subclasses of list) hasn't used __getitem__ since Python 2.2. http://www.python.org/doc/2.2/lib/typeiter.html In [7]: class circular_list(list): ...: def __getitem__(self, i): ...: return list.__getitem__(self, i%len(self)) ...: In [8]: items = circular_list(range(8)) In [9]: for i in items: ...: print i ...: 0 1 2 3 4 5 6 7 In fact, if all you need is iteration, use itertools.cycle(). In [6]: itertools.cycle? Type: type Base Class: <type 'type'> String Form: <type 'itertools.cycle'> Namespace: Interactive File: /Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/lib-dynload/itertools.so Docstring: cycle(iterable) --> cycle object Return elements from the iterable until it is exhausted. Then repeat the sequence indefinitely. In [11]: class better_circular_list(circular_list): ....: def __iter__(self): ....: return itertools.cycle(list.__iter__(self)) ....: In [13]: bcl = better_circular_list(range(8)) In [14]: for i in bcl: ....: print i ....: 0 1 2 3 4 5 6 7 0 1 2 <etc.> -- Robert Kern [EMAIL PROTECTED] "In the fields of hell where the grass grows high Are the graves of dreams allowed to die." -- Richard Harter -- http://mail.python.org/mailman/listinfo/python-list
