Project Gradebook

In this excercise
we have to add/modify one value in the last list item.
As i understand the task correctly we have to put 98 value to the last list item.
It works fine when one types
gradebook[-1] = 98
it’s also works fine when you type
gradebook[7] = 98
Why is that? The last list item should be # 5 (as we count from 0) not 7.
And why we can’t modify it using
gradebook[5][1] = 98? Which looks correct.

Step 7?

gradebook[7] = 98 doesn’t work. You get a “list assignment index out of range” error.

You have to access both indicies in the two dimensional list to change the score to 98. So, gradebook[-1] = 98 also wouldn’t work.

gradebook[5][1] = 98 works as does
gradebook[-1][-1] = 98

Somehow they work in the excercise.I wouldn’t post these lines of code if they didn’t work.

Here’s a screen where gradebook’s value is -1

here’s another screen where gradebook’s value is 7

As you can see, both codes work fine, there’s no error.

Hi aggy_m,

Setting gradebook[7] = 98 works in your code because gradebook has a length of 8 on line 11.

When you originally create gradebook on line 6, it has a length of 4.

After that, each time you call gradebook.append() on lines 7-10 the length of gradebook increases by 1.

Try printing gradebook with print(gradebook) just before line 11. You can also print its length with print(len(gradebook)).

You can see in lisalisaj’s code gradebook only has a length of 5 when they tried to assign gradebook[7] = 98, so they get an IndexError.