Exception

    IndentationError: unexpected indent
    SyntaxError: invalid syntax

    a = int(input('dividend: '))
    b = int(input('divisor: '))
    print(a/b)

    ZeroDivisionError: int division or modulo by zero

    while True:
        a = int(input('dividend: '))
        b = int(input('divisor: '))
        if b != 0:
            break

    print(a/b)

    while True:
        try:
            a = int(input('dividend: '))
            b = int(input('divisor: '))
            print('division is: ', a/b)
            print('division success, now leave program.')
            break
        except ValueError:
            print("please input a number, try again.")
        except ZeroDivisionError:
            print("divisor can't be zero, try again.")

    while True:
        try:
            # put code that can lead exception inside try.
            a = int(input('dividend: '))
            b = int(input('divisor: '))
            print('division is: ', a/b)
        except ValueError:
            print("please input a number, try again.")
        except ZeroDivisionError:
            print("divisor can't be zero, try again.")
        else:
            # put code that must be done when no exception.
            print('division success, now leave program.')
            break
        finally:
            # always done whether there are exception or not!
            print('--------------------')

    raise NameError("Don't Panic")
    # your program will show this:
    #   Traceback (most recent call last):
    #     File "<stdin>", line 1, in ?
    #   NameError: Don't Panic

    Exception    # prototype

    IOError      # no file to open
    EOFError     # no char in file left for read

    NameError    # variable does not exist
    ValueError   # operation on inappropriate value
    TypeError    # operation on inappropriate type

    RuntimeError # not in other categories

    class MyError(Exception):
         def __init__(self, value):
             '''init class with a value of exception'''
             self.value = value
         def __str__(self):
             '''exception description e.g.
             IamError: value'''
             return repr(self.value)