stopiteration

There are several ways to break out of a few nested loops They are: 1) to use break-continue for x in xrange(10): for y in xrange(10): print x*y if x*y > 50: break else: continue # only executed if break was not used break 2) to use return def foo(): for x in range(10): for y in range(10): print x*y if x*y > 50: return foo() 3) to use special exception class BreakIt(Exception): pass try: for x in range(10): for y in range(10): print x*y if x*y > 50: raise BreakIt except BreakIt: pass I had some thought that there could be some other way to do it. It is by using StopIteration exception sent

i have a generator where i would like to add an initial and final value to the actual content, it's something like this: # any generic queue where i would like to get something from q = Queue() def gen( header='something', footer='anything' ): # initial value header yield header for c in count(): # get from the queue i = q.get() # if we don't have any more data from the queue, spit out the footer and stop if i == None: yield footer raise StopIteration else: yield i Of course, the above code doesn't work - my problem is that i would like it such that when there's nothing left in the queue, i

I am using generators to perform searches in lists like this simple example: >>> a = [1,2,3,4] >>> (i for i, v in enumerate(a) if v == 4).next() 3 (Just to frame the example a bit, I am using very much longer lists compared to the one above, and the entries are a little bit more complicated than int . I do it this way so the entire lists won't be traversed each time I search them) Now if I would instead change that to i == 666 , it would return a StopIteration because it can't find any 666 entry in a . How can I make it return None instead? I could of course wrap it in a try ... except clause,

Could someone help me understand what PEP479 is about? I was reading the doc and couldn't get my head around it. The abstract says: This PEP proposes a change to generators: when StopIteration is raised inside a generator, it is replaced it with RuntimeError. (More precisely, this happens when the exception is about to bubble out of the generator's stack frame.) So for example, does a loop like so still work? it = iter([1,2,3]) try: i = next(it) while True: i = next(it) except StopIteration: pass Or does it mean that if I have a generator definition like so: def gen(): yield from range(5)