Breeds of dogs
# Make sure you understand class syntax
class Dog:
# Bark is a method that dogs have / can do. Note the indentation.
# Self is the placeholder argument referring to "this" object
# (e.g. lassie or bibi, or whoever the dog is.)
def bark(self):
print "woof"
def wag(self):
print "wag wag wag"
# Note that Dachshund is a subclass of Dog.
# Dog, however, wasn't a subclass of anything more general.
class Dachshund(Dog):
def dig(self):
print "dig dig dig"
def bark(self):
print "arf arf"
# Like Dachshunds, Collies are dogs
class Collie(Dog):
# rescue is a method that has two arguments:
# The object itself and a person name.
def rescue(self, person):
print "Come quickly, " + person + " fell down the mineshaft"
# The test program. Contains a deliberate error and will crash on final line.
def dogShow():
# We create objects by using the constructor, which is a
# "function" with the same name as the class and no arguments.
# Note the convention that class and constructor names ALWAYS
# start with a capital letter, whereas objects (instances) don't.
bibi = Dachshund()
# Note that when called, the value of the self parameter (bibi or lassie)
# moves from inside the parentheses and precedes the dot.
bibi.bark() # Should sound like "arf arf"
lassie = Collie()
lassie.bark() # Should sound like "woof"
bibi.dig() # Works ok.
lassie.rescue("Timmy") # Should do a Lassie-type thing
lassie.dig() # Should fail with an error. Dig is not something Collie's can do.
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