On Wed, Nov 4, 2009 at 7:17 PM, Hugo Arts <hugo.yo...@gmail.com> wrote: > On Wed, Nov 4, 2009 at 5:38 PM, spir <denis.s...@free.fr> wrote: >> Hello, >> >> as I was crawling in endless complications with unadequate ranges, I decided >> to create a "PolyRange" type able to hold arbitrary many "sub-range"; which >> means finally a big range with wholes in it. This whole stuff again to cope >> with unicode -- a poly-range would be able to hold a range for a char class >> (eg 'letter') which spans over several ordinal ranges. (Viva unicode >> consortium!) >> >> So, it works as needed. It is even able to "stretch" over addictional >> sub-ranges or to "unite" with a poly-range brother (sister, too). See code >> below. >> >> Now, I need it to be properly iterable if needed -- the main use beeing >> indeed the 'in' operator -- but who knows. So, I tried to implement __iter__ >> and next (by the way, why isin't it called __next__ instead, looks strange >> for a python builtin?). Seems to work, but the result looks veeery heavy to >> my eyes. As I had never written an iterator before, would be nice and >> criticize the code? >> > > You're right, next() should really be called __next__(), and this is > actually fixed in python 3 (don't know why it wasn't originally done > this way). > > Now, the code. If you write __iter__ as a generator, you won't have to > write a next method at all. It simplifies The thing a whole lot: > > def __iter__(self): > for range in self.ranges: > for item in range: > yield item > > That's it. Alternatively, you could turn the whole thing into a > one-liner and just return a generator expression from __iter__: > > def __iter__(self): > return (item for r in self.ranges for item in r) > > It's not as clear though, and it doesn't save that much space. I like > the first one slightly better. > > python documentation on generators: > http://docs.python.org/tutorial/classes.html#generators
I dont know much about generators, but this link was posted earlier this week and i learnt alot from it (actually some basics, like what happens when you iterate over different objects!) http://www.dabeaz.com/generators-uk/ (its the PDF presentation) Stefan _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
