TypeError: string indices must be integers

[ndc85430]

Why do you assume the problem is with i?

The error message talks about an index - i isn't being used as an index. However, 'question' is, so it looks like

Output:
key

is a string.

In cases like this, if it isn't at first glance obvious where the error is coming from, break down the expression into several parts. That way, the error will come from a more specific place.