### Chapter 4.3 - Modifying and summing a list

4.3 - Modifying and summing a list

So how can we add all the items in a list?

Copy the following code to Thonny and save it as sumlist:

# Add items of a list my_list = [5,76,8,5,3,3,56,5,23] # Initial Sum should be zero list_total = 0 # Loop from 0 up to the number of elements # in the array: for i in range(len(my_list)): # Add element 0, next 1, then 2, etc. list_total += my_list[i] # Print the result print(list_total)

Take a closer look to the command range(len(my_list)). What do you think it does?

We can change the code to the following. Copy and paste it again to Thonny and save it as sumlist2 :

# Add items of a list my_list = [5, 76, 8, 5, 3, 3, 56, 5, 23] # Initial Sum should be zero list_total = 0 # Loop through array, copying each item in the array into # the Variable named item. for item in my_list: # Add each item list_total += item # Print the result print(list_total)

Try to find the differences of the two previous codes.

As an exercise write a code to create a list of all integer numbers from 11 to 81 and then calculate the sum of this list. You should find 3266

Steps

1. create an empty list with any name (ex. new_list)
2. with a for loop append numbers from 11 to 81 to the list
3. create a variable total to sum the numbers and initiate it to 0
4. with a new for loop add all items of the list to total variable

The solution can be found here.