"""This demonstration sets up a number of objects of
type "thingy" and compares them - see comments for how
each type of comparison works"""

class thingy(object):
    def __init__(self,about,edible="no"):
        self.about = about
        self.edible = edible
    def __eq__(this,that):
        return this.about == that.about
    def __str__(self):
        return "A thingy which is "+self.about+" and with an edibility "+self.edible

if __name__ == "__main__":

    def say(test,vlue):
        print(test + " " + str(vlue))

    toothpaste = thingy("sticky")
    toffeepudding = thingy("sticky","yes")
    jamrollypolly = thingy("sticky","yes")
    forum_topic = thingy("sticky")
    water = thingy("wet")
    mydesert = toffeepudding

    say("toothpaste:",toothpaste)
    say("toffeepudding:",toffeepudding)
    say("jamrollypolly",jamrollypolly)
    say("forum_topic:",forum_topic)
    say("water:",water)
    say("mydesert:",mydesert)

# Testing equality - which is NOT checking for identicalness
# on your own class unless you set it up to do so.

# So two things can be "equal" even if they produce diffent strings

    print("\nUse of ==, showing that == does NOT mean identity")

    if toothpaste == toffeepudding:
        print("Toothpaste and Toffeepudding are equal")
    else:
        print("Toothpaste and Toffeepudding are NOT equal")

    if water == toffeepudding:
        print("Water and Toffeepudding are equal")
    else:
        print("Water and Toffeepudding are NOT equal")

# If you are wanting to test whether two objects are one and the same
# (i.e. if the variable point to the same pieces of memory) you cannot
# rely on ==, nor on the string conversion ...

    print("\nComparing the print strings - does not test for same object")
    if str(toothpaste) == str(forum_topic):
        print("toothpaste and forum_topic are the same")
    if str(toffeepudding) == str(mydesert):
        print("toffeepudding and mydesert are the same")

# ... but you CAN usually rely on the __repr__ method which gives you
# the official string representation of an object, and which is also
# accessible through the backquote in Python 2 (gone in Python 3)

# Now you shoud use the id function or the is keyword

    print("\nCompare two objects via __repr__ - are they the same object")
    if toffeepudding is jamrollypolly:
        print("toffeepudding and jamrollypolly are refs to same object")
    if toffeepudding is mydesert:
        print("toffeepudding and mydesert are identical refs to same object")
    say("toffeepudding:",toffeepudding)
    say("mydesert:",mydesert.__repr__())
    say("jamrollypolly:",jamrollypolly.__repr__())

""" Sample outputs

WomanWithCat:y106 grahamellis$ python3 rr2
toothpaste: A thingy which is sticky and with an edibility no
toffeepudding: A thingy which is sticky and with an edibility yes
jamrollypolly A thingy which is sticky and with an edibility yes
forum_topic: A thingy which is sticky and with an edibility no
water: A thingy which is wet and with an edibility no
mydesert: A thingy which is sticky and with an edibility yes

Use of ==, showing that == does NOT mean identity
Toothpaste and Toffeepudding are equal
Water and Toffeepudding are NOT equal

Comparing the print strings - does not test for same object
toothpaste and forum_topic are the same
toffeepudding and mydesert are the same

Compare two objects via __repr__ - are they the same object
toffeepudding and mydesert are identical refs to same object
toffeepudding: A thingy which is sticky and with an edibility yes
mydesert: <__main__.thingy object at 0x10063a860>
jamrollypolly: <__main__.thingy object at 0x10063a898>
WomanWithCat:y106 grahamellis$

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

WomanWithCat:y106 grahamellis$ python2 rr2
toothpaste: A thingy which is sticky and with an edibility no
toffeepudding: A thingy which is sticky and with an edibility yes
jamrollypolly A thingy which is sticky and with an edibility yes
forum_topic: A thingy which is sticky and with an edibility no
water: A thingy which is wet and with an edibility no
mydesert: A thingy which is sticky and with an edibility yes

Use of ==, showing that == does NOT mean identity
Toothpaste and Toffeepudding are equal
Water and Toffeepudding are NOT equal

Comparing the print strings - does not test for same object
toothpaste and forum_topic are the same
toffeepudding and mydesert are the same

Compare two objects via __repr__ - are they the same object
toffeepudding and mydesert are identical refs to same object
toffeepudding: A thingy which is sticky and with an edibility yes
mydesert: <__main__.thingy object at 0x10eb3f690>
jamrollypolly: <__main__.thingy object at 0x10eb3f6d0>
WomanWithCat:y106 grahamellis$

"""