Re: Is there a better way to code variable number of return arguments?
On Thursday, 8 October 2009 18:41:31 Dr. Phillip M. Feldman wrote: I currently have a function that uses a list internally but then returns the list items as separate return values as follows: if len(result)==1: return result[0] if len(result)==2: return result[0], result[1] (and so on). Is there a cleaner way to accomplish the same thing? Why do you not change the list into a tuple and return the tuple, and let automatic unpacking handle it? As I see it, the problem is not in the return, but in the call - how do you know now, which of the following to write: answer = thing(params) answer0,answer1 = thing(params) answer0,answer1,answer2 = thing(params) answer0,answer1,answer2,answer3 = thing(params) and so on... probably best to write: answers = thing(params) for answer in answers: do something with answer - Hendrik -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way to code variable number of return arguments?
Dr. Phillip M. Feldman schrieb: I currently have a function that uses a list internally but then returns the list items as separate return values as follows: if len(result)==1: return result[0] if len(result)==2: return result[0], result[1] (and so on). Is there a cleaner way to accomplish the same thing? You can simply return result. If you want to make sure that you return a copy of the internal list, do return list(result) or return tuple(result). Christian -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way to code variable number of return arguments?
Dr. Phillip M. Feldman wrote: I currently have a function that uses a list internally but then returns the list items as separate return values as follows: if len(result)==1: return result[0] if len(result)==2: return result[0], result[1] (and so on). Is there a cleaner way to accomplish the same thing? return tuple(result) But you down want to do that, cause the caller will have a hell of a job getting your result. You may want to simply return the list itself. JM -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way to code variable number of return arguments?
Paul Rubin wrote: Ethan Furman et...@stoneleaf.us writes: some_list = [1, 2] this, that = func(alist) At least, in 2.5.4 this works. :-) But that fails if there are fewer than two elements in the list. It's better to just make the logic either expect a list, or if it's implementing something like an optional value, code it up explicitly. You may even want to return two lists, the second one possibly empty. It also fails if there are more than two elements in the list, as the rest of my post went on to say. I myself would generally not use such a structure, but that doesn't mean the OP doesn't have a good use case for it. Don't forget, his original question indicated that there could be more than two return elements also. ~Ethan~ -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way to code variable number of return arguments?
Dr. Phillip M. Feldman wrote: I currently have a function that uses a list internally but then returns the list items as separate return values as follows: if len(result)==1: return result[0] if len(result)==2: return result[0], result[1] (and so on). Is there a cleaner way to accomplish the same thing? How about using yield and then iterate over the answer: def some_fun(): \tfor result in some_loopable_stuff: \t\t yield result Then call it thusly: for i in some_fun() result = i -Jack (PS, sorry to the OP, you will get two of these -- I forgot to CC the list) -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way to code variable number of return arguments?
I'm amazed that this works. I had not realized that x,y= [3,4] is equivalent to x= 3; y= 4 Python is rather clever. Thanks! snip To elaborate on Paul's answer, returning the list will also unpack it if you have it set up that way. E.g. def func(alist): return alist some_list = [1, 2] this, that = func(alist) At least, in 2.5.4 this works. :-) Mind you, if you don't have the correct number of return names to match the unpacking you'll get the normal errors from that. Hope this helps! ~Ethan~ -- http://mail.python.org/mailman/listinfo/python-list -- View this message in context: http://www.nabble.com/Is-there-a-better-way-to-code-variable-number-of-return-arguments--tp25803294p25813206.html Sent from the Python - python-list mailing list archive at Nabble.com. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way to code variable number of return arguments?
This is an interesting alternative. If one wants to generate everything and return it at one shot, the list approach is better, but there are situations where generating things incrementally is preferrable, e.g., because the caller doesn't know a priori how many things he wants. I will try this out. Thanks! Jack Norton wrote: Dr. Phillip M. Feldman wrote: I currently have a function that uses a list internally but then returns the list items as separate return values as follows: if len(result)==1: return result[0] if len(result)==2: return result[0], result[1] (and so on). Is there a cleaner way to accomplish the same thing? How about using yield and then iterate over the answer: def some_fun(): \tfor result in some_loopable_stuff: \t\t yield result Then call it thusly: for i in some_fun() result = i -Jack (PS, sorry to the OP, you will get two of these -- I forgot to CC the list) -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way to code variable number of return arguments?
Dr. Phillip M. Feldman wrote: I'm amazed that this works. I had not realized that x,y= [3,4] is equivalent to x= 3; y= 4 Python is rather clever. Thanks! snip To elaborate on Paul's answer, returning the list will also unpack it if you have it set up that way. E.g. def func(alist): return alist some_list = [1, 2] this, that = func(alist) At least, in 2.5.4 this works. :-) In just about all Python versions for all sequence types, in fact. Mind you, if you don't have the correct number of return names to match the unpacking you'll get the normal errors from that. Yes. This is why people are suggesting that you be consistent about what you return. This is quite different from Matlab where the interpreter knows how many return values the caller is expecting in order to overload functions, but I think it makes for much more understandable code. -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way to code variable number of return arguments?
Dr. Phillip M. Feldman writes: I currently have a function that uses a list internally but then returns the list items as separate return values as follows: if len(result)==1: return result[0] if len(result)==2: return result[0], result[1] (and so on). Is there a cleaner way to accomplish the same thing? The suggestions to return result or if needed tuple(result) are good, if a sequence is expected. But perhaps better if each element has separate meaning: return a defaultdict; document the keys. http://docs.python.org/library/collections.html#collections.defaultdict Cheers, Alan Isaac -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way to code variable number of return arguments?
On Thu, Oct 8, 2009 at 7:14 PM, Dr. Phillip M. Feldman pfeld...@verizon.net wrote: I'm amazed that this works. I had not realized that x,y= [3,4] is equivalent to x= 3; y= 4 Python is rather clever. Thanks! Python is very clever: (a, b), c = (1, 2), 3 a, b, c (1, 2, 3) :D -- http://mail.python.org/mailman/listinfo/python-list
