Excellent, thanks for that answer Kent. Also thanks for the link
2009/6/18 Kent Johnson <ken...@tds.net>: > On Thu, Jun 18, 2009 at 6:21 AM, karma<dorjeta...@googlemail.com> wrote: >> Hi All, >> >> I'm trying to write a function that flattens a list. However after I >> call the function more than once, it appends the result (a list) from >> the second call with the first. I can get around it by either setting >> the list to an empty one before calling the function, but I would like >> to keep it in the function, another alternative I found was to pass an >> empty list as an argument. >> >> Can someone explain how python keeps track of variables within >> functions (I was expecting the variable to be destroyed after a value >> was returned). Also what is a better way to handle this? > > Default arguments are only evaluated once, when the function is > compiled, so the start list is shared between invocations of flatten. > This is a FAQ: > http://effbot.org/pyfaq/why-are-default-values-shared-between-objects.htm > > Another solution - it's easy to rewrite flatten() so it doesnt' need a > default argument: > > In [1]: def flatten(myList): > ...: start = [] > ...: for i in myList: > ...: if type(i) != list: > ...: start.append(i) > ...: else: > ...: start.extend(flatten(i)) > ...: return start > > Kent > > PS Please don't quote unrelated questions when posting. > >> Thanks _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
