Raising an Exception

'raise' Keyword:

You can raise any Exception (Built-in + Custom) by using 'raise' keyword.

You can pass message inside raised Exception that designates the problem.

syntax: raise [ExceptionName](optional_message)

try:
	n = int(input("Enter the number for factorial:"))
	if n < 0:
		raise ValueError("Number cannot be negative")
	#factorial code here
except Exception as obj:
	print(obj)

In above example, raise statement will be executed if user enters number less than 0. This statement will raise ValueError and control goes to except block. "Number cannot be negative" will be passed to obj and got printed on console.