Python (2nd Edition): Learn Python in One Day and Learn It Well. Python for Beginners with Hands-on Project. (Learn Coding Fast with Hands-On Project Book 1)

Python is a widely used high-level programming language created by Guido van Rossum in the late 1980s.

The notation 2:4 is known as a slice. Whenever we use the slice notation in Python, the item at the start index is always included, but the item at the end is always excluded. Hence the notation 2:4 refers to items from index 2 to index 4-1 (i.e. index 3), which is why userAge3 = [23, 24] and not [23, 24, 25].