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titaniumdecoy · Jun 7th, 2006, 6:37 PM

I have been learning Python for a while now. I was browsing old posts in this forum and stumbled across this thread in which Arevos posted the following code:

(Toggle Plain Text)

def permutations(x):
    if len(x) <= 1:
        yield x
    else:
        for i in range(len(x)):
            for p in permutations(x[:i] + x[i + 1:]):
                yield [x[i]] + p

I understand recursion, but what is yield and how does it differ from return? And what is a recursive generator?

Also, I understand the gist of how this function works, but it is more complicated than most recursive functions I have studied. Could someone please explain how this particular function works, especially the last two lines? Thanks.

Jun 7th, 2006, 6:37 PM	#1
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 841 Rep Power: 3	Recursion: yield vs. return I have been learning Python for a while now. I was browsing old posts in this forum and stumbled across this thread in which Arevos posted the following code: (Toggle Plain Text) def permutations(x): if len(x) <= 1: yield x else: for i in range(len(x)): for p in permutations(x[:i] + x[i + 1:]): yield [x[i]] + p def permutations(x): if len(x) <= 1: yield x else: for i in range(len(x)): for p in permutations(x[:i] + x[i + 1:]): yield [x[i]] + p I understand recursion, but what is yield and how does it differ from return? And what is a recursive generator? Also, I understand the gist of how this function works, but it is more complicated than most recursive functions I have studied. Could someone please explain how this particular function works, especially the last two lines? Thanks.