Inheritance & Exceptions

1. Inheritance:

 - superclass vs subclass:
  

  class DerivedClassName(BaseClassName):

  class DerivedClassName(modname.BaseClassName): 

  e.g.class IntStack(Stack): 

- built-in functions that work with inheritance:

   a)Use isinstance() to check an instance’s type: isinstance(obj, int) will be True only if   obj.__class__ is int or some class derived from int.
   b)Use issubclass() to check class inheritance: issubclass(bool, int) is True since bool is a subclass of int. However, issubclass(float, int) is False since float is not a subclass of int.



2. Exceptions:

e.g. class SpecialException(Exception):
    pass

class ExtremeException(SpecialException):
    pass

if __name__ == '__main__':
    try:
        #1/0
        #raise SpecialException('I am a SpecialException')
        #raise Exception('I am an Exception')
        raise ExtremeException('I am an ExtremeException')
        #1/0
    except SpecialException as se:
        print(se)
        print('caught as SpecialException')
        raise
    except ExtremeException as ee:
        print(ee)
        print('caught as ExtremeException')
        #raise
    except Exception as e:
        print(e)
        print('caught as Exception')


Lab: Final question was solved by not shifting every positions after pop, but add 1 index to every elements, which saves operating time :)

19.5. Glossary

exception

An error that occurs at runtime.

handle an exception

To prevent an exception from causing our program to crash, by wrapping the block of code in a try ... except construct.

raise

To create a deliberate exception by using the raise statement.