[EMAIL PROTECTED] wrote: > Often I need to tell the len of an iterator, this is a stupid example: > > >>> l = (i for i in xrange(100) if i&1) > > len isn't able to tell it: > > >>> len(l) > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: object of type 'generator' has no len() > > This is a bad solution, it may need too much memory, etc: > > >>> len(list(l)) > > This is a simple solution in a modern Python: > > >>> sum(1 for _ in l) > 50 > > This is a faster solution (and Psyco helps even more): > > def leniter(iterator): > """leniter(iterator): return the length of an iterator, > consuming it.""" > if hasattr(iterator, "__len__"): > return len(iterator) > nelements = 0 > for _ in iterator: > nelements += 1 > return nelements > > Is it a good idea to extend the functionalities of the built-in len > function to cover such situation too? > > Bye, > bearophile
Is this a rhetorical question ? If not, try this: >>> x = (i for i in xrange(100) if i&1) >>> if leniter(x): print x.next() George -- http://mail.python.org/mailman/listinfo/python-list
