Raise, customised an Exception

Some users might miuse the function we have written; then, we should raise an exception for them to catch.

All exceptions inherited from BaseException. Customise exceptions should inherit BaseException too. (Otherwise, we will get TypeError)

class NegativeNumberException(BaseException):
	def __init__(self, age):
		super().__init__()
		self.age = age
		if (age < 0):
			print("This is not a valid age!!!")

def enter_age(age):
	if age < 0:
		raise NegativeNumberException(age)

	if age % 2 == 0:
		print("Your age is an even number.")
	else:
		print("Your age is odd.")

-------------------------------------------------------------------

import something

try:
	num = 33
	something.enter_age(num)
except something.NegativeNumberException as error:
	print(error)
except:
	print("Something we don't know went wrong...")

#If you enter the age smaller than 0, 
#you will get the message about This is not a valid age.

#The valid number you entered will mode 2, the result will be an even or odd.
#Enter non integer value trigered error wiht a message 
#Something we don't know went wrong...

Order of Exception

The order of putting exception codes matters!

Parent class:

1. LookupError

Child class:

1. IndexError (happen in list)
2. KeyError (happen in dict)

#Child classes after Parent will never be implemented.