Give this a shot
def snap(keyword, words):
matches = [i for i, s in enumerate(words) if s.startswith(keyword)]
for i in matches:
lst.insert(0, lst.pop(i))
Your current implementation is reassigning the local variable ``mylist`` to
a new list inside the function.
On Fri, Apr 1, 2016 at 4:30 PM Fillmore <fillmore_rem...@hotmail.com> wrote:
>
> notorious pass by reference vs pass by value biting me in the backside
> here. Proceeding in order.
>
> I need to scan a list of strings. If one of the elements matches the
> beginning of a search keyword, that element needs to snap to the front
> of the list.
> I achieved that this way:
>
>
> for i in range(len(mylist)):
> if(mylist[i].startswith(key)):
> mylist = [mylist[i]] + mylist[:i] + mylist[i+1:]
>
> Since I need this code in multiple places, I placed it inside a function
>
> def bringOrderStringToFront(mylist, key):
>
> for i in range(len(mylist)):
> if(mylist[i].startswith(key)):
> mylist = [mylist[i]] + mylist[:i] + mylist[i+1:]
>
> and called it this way:
>
> if orderstring:
> bringOrderStringToFront(Tokens, orderstring)
>
> right?
> Nope, wrong! contrary to what I thought I had understood about how
> parameters are passed in Python, the function is acting on a copy(!) and
> my original list is unchanged.
>
> I fixed it this way:
>
> def bringOrderStringToFront(mylist, key):
>
> for i in range(len(mylist)):
> if(mylist[i].startswith(key)):
> mylist = [mylist[i]] + mylist[:i] + mylist[i+1:]
> return(mylist)
>
> and:
>
> if orderstring:
> Tokens = bringOrderStringToFront(Tokens, orderstring)
>
> but I'm left with a sour taste of not understanding what I was doing
> wrong. Can anyone elaborate? what's the pythonista way to do it right?
>
> Thanks
>
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> https://mail.python.org/mailman/listinfo/python-list
>
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