I am stuck on this challenge! I just don't get it. help!

Putting the Fun Back in Functions Challenge Part 1 of 2:

Make a function named add_list that takes a list. The function should then add all of the items in the list together and return the total. Assume the list contains only numbers.

Let's take it step-by-step.

Make a function named add_list that takes a list

The instructions might be said as "Make a function named add_list that takes a single argument. The function can expect the argument to be a list. The function below takes a single argument.

def add_list(list_in):
  # this function does nothing but return
  return

The function should then add all of the items in the list together.... Return total

def add_list(list_in):
    # initialize result to zero
    result = 0
    # for each item in list_in
    for value in list_in:
        # add item to result
        result = result + value
    # return total
    return result

The statement result = result + value can be abbreviated as result += value.

Challenge Task 2 of 2 :

Now, make a function named summarize that also takes a list. It should return the string "The sum of X is Y.", replacing "X" with the string version of the list and "Y" with the sum total of the list.

def summarize(list_in):
    # Set X to input list
    X = list_in
    # Set Y to sum of items in list using add_list() function
    Y = add_list(list_in)
    # return string
    return "The sum of {} is {}".format(X, Y)

This can be compress into a single statement:

def summarize(list_in):
  return "The sum of {} is {}".format(list_in, add_list(list_in))