problematic python function returns

I have a function similar to the following:

def getCost(list):
  cost = 0
  for item in list:
    cost += item
  return cost

and I call it as so:

cost = getCost([1, 2, 3, 4])

This is GREATLY simplified but it illustrates what is going on. No matter what I do, cost always ends up == 0. If I change the value of开发者_StackOverflow社区 cost in the function to say 12, then 12 is returned. If I debug and look at the value of cost prior to the return, cost == 10

It looks like it is always returning the defined number for cost, and completely disregarding any modifications to it. Can anyone tell me what would cause this?

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This should solve all of your problems (if summing the list items in cost is indeed what you're trying to do:

def getCost(costlist):
    return sum(costlist)

It accomplishes the exact same things and is guaranteed to work. It's also much more simple than using a loop and an accumulator.