list indices must be integers or slices, not str

This error occurs when you try to use a string as an index for a list or sequence. In Python, list indices must be integers or slices, which means that they cannot be strings.

For example, if you have a list called `my_list` and you try to access an element using a string as an index like this:

my_list['hello']

You will get the "list indices must be integers or slices, not str" error.

To fix this error, you need to use an integer or a slice as the index. For example:

my_list[0] # access the first element of the list
my_list[1:3] # access a slice of the list from the second to the third element

If you need to convert a string to an integer to use it as an index, you can use the `int()` function:

index = int('2')
my_list[index] # access the third element of the list