Study help for Python!

[Yoo Song Won]

I'm not really sure what the values in the square brackets means in both of these short programs. Can someone please explain the purpose of them? 

In this one, what does the "[ i ]" do in "totalSum = totalSum + numbers[ i ]"

In this second one, what does the [0] and [1:] do in "return numbers[0] + addNums(numbers[1:])" 

 

Please can you help me in the simplest terms possible? Thank you very much in advance!

[Lurick]

i is an iteration. Look at the 'marks' list, you have 5 values defined. It's kind of like saying iterate through this loop a number of times equal to the number of references which python figures out with the "len(numbers)" part. When you get to the totalSum + numbers part it tells python which value in the list to use from the 'marks' list variable. So the first time it adds 0 + 3, then 3 + 6, then 9+2... and so on.

[BobVonBob]

Those are list locations, accessing list[x] will give the x-th item in the array, starting at 0. The [1:] is a special case of this for python and languages like it called slice notation, it's a slightly more complex list location that essentially says "every item from the 1st location to the last" in this case (1st location is the 2nd item, because arrays start at 0)

 

Check out https://www.learnpython.org/en/Lists for a beginner rundown on all this stuff.