As others answered, Python generally doesn't raise an exception for out-of-range slices. However, and this is important, your slice is not out-of-range. Slicing is specified as a closed-open interval, where the beginning of the interval is inclusive, and the end point is exclusive.
In other words, [2:3] is a perfectly valid slice of a three-element list, that specifies a one-element interval, beginning with index 2 and ending just before index 3. If one-after-the-last endpoint such as 3 in your example were illegal, it would be impossible to include the last element of the list in the slice.
