Iterating over arrays in Python 3

Question

I haven't been coding for awhile and trying to get back into Python. I'm trying to write a simple program that sums an array by adding each array element value to a sum. This is what I have:

def sumAnArray(ar):     theSum = 0     for i in ar:         theSum = theSum + ar[i]     print(theSum)     return theSum 

I get the following error:

line 13, theSum = theSum + ar[i] IndexError: list index out of range 

I found that what I'm trying to do is apparently as simple as this:

sum(ar) 

But clearly I'm not iterating through the array properly anyway, and I figure it's something I will need to learn properly for other purposes. Thanks!

Answer 1

When you loop in an array like you did, your for variable(in this example i) is current element of your array.

For example if your ar is [1,5,10], the i value in each iteration is 1, 5, and 10. And because your array length is 3, the maximum index you can use is 2. so when i = 5 you get IndexError. You should change your code into something like this:

for i in ar:     theSum = theSum + i 

Or if you want to use indexes, you should create a range from 0 ro array length - 1.

for i in range(len(ar)):     theSum = theSum + ar[i]