What is the raise expression in Python and how is it used?

In Python, the keyword raise is used to generate exceptions (errors) during program execution. It allows explicitly interrupting the normal flow of execution and passing control to an exception handler.

Example of usage:

def divide(a, b):
    if b == 0:
        raise ValueError("Division by zero is not possible")
    return a / b

try:
    result = divide(10, 0)
except ValueError as e:
    print(f"Error: {e}")

Here, raise creates a ValueError exception, which can be caught and handled in the except block. This helps control errors and makes the code more reliable.