Section #8.md

Task: Write a Python script to model a simple zoo system using object-oriented programming concepts.

Step 1: Define Custom Exception Class

1. Begin by defining a custom exception class named AnimalNotFoundError.
2. Implement the init method to initialize the exception with the name of the animal not found.
3. Override the str method to return a formatted error message.

Step 2: Define Animal Classes

1. Create a base class named Animal.
2. Implement the init method to initialize each animal with a name and age.
3. Define getter methods get_name() and get_age() to retrieve the name and age of an animal.
4. Define the make_sound() method as a placeholder method for producing animal sounds.
5. Implement the info() method to return information about the animal (name and age).

Step 3: Define Subclasses

1. Create subclasses Dog and Cat inheriting from the Animal class.
2. Implement the init method for each subclass to initialize additional attributes (breed for Dog and color for Cat).
3. Define getter methods get_breed() for Dog and get_color() for Cat to retrieve specific attributes.
4. Override the make_sound() method in each subclass to produce the appropriate sound for the animal.
5. Override the info() method in each subclass to include additional information specific to the animal type.

Step 4: Define Zoo Class

1. Create a class named Zoo to manage the animals in the zoo.
2. Implement the init method to initialize an empty list to store animals.
3. Define an add_animal() method to add an animal to the zoo.
4. Implement two overloaded get_animal_by_name() methods using the multipledispatch decorator:
   • One method takes a string parameter to search for an animal by name.
   • Another method takes an object parameter to search for an animal by object reference.
5. Implement make_sound_generic() and print_info_generic() methods to iterate over all animals and print their sounds and information.

Step 5: Define Duck Typing Function

1. Define a function named print_obj_data() to demonstrate duck typing.
2. This function takes an object as a parameter and calls the make_sound() and info() methods of the object.

Step 6: Main Execution

1. Inside the if name == "main": block:
   • Create instances of Dog and Cat.
   • Create a Zoo instance and add the animals to the zoo.
   • Call the make_sound_generic() and print_info_generic() methods of the zoo.
   • Demonstrate polymorphism by using the get_animal_by_name() method to retrieve animals by name and object reference.
   • Print the sound and information of the retrieved animals using the print_obj_data() function.
   • Handle AnimalNotFoundError exceptions if an animal is not found in the zoo.

Note: By following these steps, students can create a Python script that models a simple zoo system using object-oriented programming principles and demonstrate their understanding of concepts such as inheritance, polymorphism, dynamic binding, and exception handling.

• Solution:

from multipledispatch import dispatch


class AnimalNotFoundError(Exception):
    def init(self, name):
        self.name = name

    def str(self):
        return f"Animal '{self.name}' not found in the zoo."

class Animal:
    def init(self, name, age):
        self._name = name
        self._age = age

    def get_name(self):
        return self._name

    def get_age(self):
        return self._age

    def make_sound(self):
        pass

    def info(self):
        return f"{self._name} is {self._age} years old."

class Dog(Animal):
    def init(self, name, age, breed):
        super().init(name, age)
        self._breed = breed

    def get_breed(self):
        return str.upper(self._breed)

    def make_sound(self):
        return "Woof!"

    def info(self):
        return f"{super().info()} He is a {self._breed}."

class Cat(Animal):
    def init(self, name, age, color):
        super().init(name, age)
        self._color = color

    def get_color(self):
        return self._color

    def make_sound(self):
        return "Meow!"

    def info(self):
        return f"{super().info()} She has {self._color} fur."

class Zoo:
    def init(self):
        self._animals = []

    def add_animal(self, animal):
        self._animals.append(animal)

    @dispatch(str)
    def get_animal_by_name(self, name):
        for animal in self._animals:
            if animal.get_name() == name:
                return animal
        return None

    @dispatch(object)
    def get_animal_by_name(self, animal_obj):
        return self.get_animal_by_name(animal_obj.get_name())

    def make_sound_generic(self):
        for animal in self._animals:
            print(animal.make_sound())

    def print_info_generic(self):
        for animal in self._animals:
            print(animal.info())


def print_obj_data(obj):
    print("duck typing function start")
    print(obj.make_sound())
    print(obj.info())
    print("duck typing function end")

if name == "main":
    dog = Dog("Buddy", 5, "Labrador")
    cat = Cat("Whiskers", 3, "White")

    zoo = Zoo()
    zoo.add_animal(dog)
    zoo.add_animal(cat)

    zoo.make_sound_generic();

    zoo.print_info_generic();

    print(zoo.get_animal_by_name("Buddy")) # address of object, first overloaded method

    print(zoo.get_animal_by_name(dog)) # address of object, second overloaded method



    print(zoo.get_animal_by_name("Buddy").get_age()) # 5 , as it returns object (dog) then call get_age() method inside it

    print(zoo.get_animal_by_name("Buddy123")) # None

    # note: we have passed an anonymous object (refer polymorphism section)
    print(zoo.get_animal_by_name(Cat("Whiskers12345", 3, "White"))) # None, as 'Whiskers12345' name is not found

    # Polymorphism with string parameter
    animal_object_copy = zoo.get_animal_by_name("Buddy")
    if animal_object_copy:
        print_obj_data(animal_object_copy)
    else:
        raise AnimalNotFoundError("Object Not Found 1")

    # Polymorphism with object parameter
    animal_obj = zoo.get_animal_by_name(cat)
    if animal_obj:
        print_obj_data(animal_obj)
    else:
        raise AnimalNotFoundError("Object Not Found 2")