[Delaney, Timothy C] > Nick's other suggestion - that genexps propagate __len__ - might > still be interesting. Of course, it would only be applicable for > unconditional genexps(i.e. no if clause).
Length transparency for iterators is not as general as one would expect. I once spent a good deal of effort exploring where it made sense, and I was surprised to find that it only rarely works out. Length transparency is an unexpectedly thorny subject with many dead-ends which precludes a fully general solution such as that proposed by Nick. For a recap of my research, see the docstring for Lib/test/test_iterlen.py . Raymond Hettinger -- http://mail.python.org/mailman/listinfo/python-list
