#!/usr/bin/env python

"""Python type checking

Simple illustration of all the various kinds of type-checking you can
do in Python.
"""

import types

def type_check_1(x):
    """Return the square of an integer

    Raise a TypeError if the argument is not an integer.
    """
    if not type(x) == types.IntType:
        raise TypeError, "%s is not an integer" % x
    return x**2


def type_check_1(x):
    """Return the square of an integer

    Raise a TypeError if the argument is not an integer.
    """
    if not type(x) == type(53):
        raise TypeError, "%s is not an integer" % x
    return x**2


# Here is a very basic object hierarchy.
#
#                object
#                  |
#                 / \
#                /   \
#               A     C
#               |
#               |
#               B
class A(object):
    pass

class B(A):
    pass

class C(object):
    pass



if __name__ == "__main__":
    # Pass in the correct argument type.
    print type_check_1(4) # 16

    # Pass in an invalid argument type.
    try:
        type_check_1([53, 'mouse', 3+2j])
    except TypeError, e:
        print e # Prints the exception

    # Illustration of object hierarchy.
    a = A()
    b = B()
    c = C()

    print type(a) # <class '__main__.A'>
    print type(b) # <class '__main__.B'>
    print type(c) # <class '__main__.C'>

    print isinstance(a, A) # True
    print isinstance(b, B) # True
    print isinstance(c, C) # True

    print isinstance(b, A) # True
    print isinstance(c, A) # False

    print issubclass(B, A) # True
    print issubclass(C, A) # False

    print issubclass(A, object) # True
    print issubclass(A, B) # False