On 04/03/16 15:00, Gaston wrote: > Both work but I am not satisfied. Is there not a method that could do > the job of '+' operator (namely concatenate in a copy)?
Why would you want a method? An operator is a perfectly legitimate feature and is at least as readable as a method. It is certainly no less "functional". And of course, in Python + usually translates to the __add__() method anyway. As to how your initial function works can I suggest you sit down with a pen and paper and work through the code iteration by iteration. Start with 2 element lists and then try 3 elements. By the time you've done that it should become clear. Keep track of the contents of list1 and list2 and the output for each call of the function. Recursive can be a seductive technique but it can be a real brain twister to work out and debug when things don;t go as expected! The pen/paper manual approach is the most reliable technique I've found. Here is what I mean for a 2 element list pair: list1 list2 f(list1,list2) ----------------------------------------------- [1] [2] f([1],[]).append(2) # first call of f() [1] [] [1].append(2) -> list1 becomes [1,2] [1,2] [] f([1,2],[]) # 2nd call of f() -> [1.2] Now try that for 2 elements per list, then 3. In effect you move elements from list 2 to list 1, or vice versa. And you iterate over the list multiple times. It's very inefficient as well as non intuitive. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
