Python

Exceptions

Python exceptions allow you to attempt code that may result in an error and execute additional functionality on said error.

• Try/except/finally/else
  • Try statement begins an exception handling block
• Raise
  • Triggers exceptions
• Except
  • Handles the exception
• Multiple Exceptions
  • Handles multiple exceptions

Example

try:
    <statements>
except: <name>:
    <statements>
except: <name> as <data>:
    <statements>
else:
    <statements>

try:
    <statements>
finally:
    <statements>

Example 2:

"""
Checks a certain range of numbers to see if they can divide into a user specified num
"""
# Program main, runs at start of program
def launch():
    num = input('What number would you like to check?')
    amount = input('How many numbers do you want to check?')

    if isInt(num) == False or isInt(amount) == False:
        print("You must enter an integer")
        launch() 
    elif int(amount) < 0 or int(num) < 0:
        print("You must enter a number greater than 0")
        launch() 
    else:
        divisible_by(int(num), int(amount))

# Checks num divisible numbers up to amount or itself
def divisible_by(num, amount):
    i = 1.0
    while (num / i >= 1 and amount > 0):
        if num % i == 0:
            print('{} is divisible by {}'.format(int(num), int(i)))
            amount -= 1
        i += 1

# EXCEPTION HANDLING
def isInt(x):
    try:
        int(x) ###
        return True
    except ValueError:
        return False

launch()

 
class CustomError(Exception):
    def _init_(self, msg):
        self.msg = msg
         
    def _str_(self):
        return "your error is {}".format(self.msg)
         
    def doStuff(danger):
        if danger == True:
            raise CustomError("Whoa don't do that!")
            print("Success") #What happens here?
 
try:
    doStuff(True)
    
except CustomError as stuff:
    print(stuff)