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Python Python Basics (Retired) Putting the "Fun" Back in "Function" Functions

Tony Brackins
Tony Brackins
28,766 Points
Posted by Tony Brackins
Tony Brackins
28,766 Points

I'm lost, please help. Make a function named add_list that adds all of the items in a passed-in list together and return

This is what I've got so far. I watched all the videos, I've followed along but I'm stuck here. Please help:

passed_in_list = [1, 2, 3]

def add_list():
  for item in passed_in_list:
    passed_in_list

4 Answers

Marko Koron
Marko Koron
20,658 Points
Marko Koron
Marko Koron
20,658 Points

I don't know the concrete problem but first of all I would define the function this way:

def add_list(sum_list):
  for item in sum_list:
    ...

then you call the function like this add_list(passed_in_list). But for your code also would work. Regarding your problem, you did start OK with the statement for item in passed_in_list, now think of what did you write after. You are looping a list, so are looking for an item on the second line, not the list. And what do you need to do with this items? Add them together, so you need a variable that will store the sum, and in the for loop it will store the the sum of all the items one by one (don't forget that you need to add the value that this variable is holding with the every new item.). After the loop ended you simply return the variable holding the sum.

Marko Koron
Marko Koron
20,658 Points
Marko Koron
Marko Koron
20,658 Points

You need to initialize the variable sum like this, sum = 0, or you will get a referenced before assignment error(remember that you are using the value of this variable in the summation "sum = sum + item", you cannot have "sum = undefined + item")

Tony Brackins
Tony Brackins
28,766 Points
Tony Brackins
Tony Brackins
28,766 Points

I'm sorry, I'm still not understanding.

I know that this is the answer and have a few questions: list=[1,2,3]

def add_list(list): sum = 0 for num in list: sum = sum + num return sum

b= add_list(list) print(b)

for "sum = 0", where did this come from?

Like, how would I know to make this statement?

Thanks,

Tony