Python Basics Exercises: Building Systems With Classes (Summary)

class Animal:
    species = "Animal"
    default_greeting = "Hello!"

    def __init__(self, name, colour):
        self.name = name
        self.colour = colour

    def __str__(self):
        return f"{self.name} is a {self.colour} {self.__class__.species.lower()}."

    def speak(self, sound=None):
        print(f"{self.name} says '{sound if sound else self.__class__.default_greeting}'")

    def move(self, source, destination):
        # Move animal from one Habitat to another by deleting from source Habitat and adding to dest Habitat
        # Could upgrade this so that the source doesn't need to be specified, but hey this is just a simple exercise
        if self in source.occupants and destination.remaining_spaces > 0:
            source.remove_animal(self)
            destination.add_animal(self)
        else:
            print(
                f"Error: Can't move {self.name} from the {source.name} to the {destination.name}: animal not present "
                f"in the {source.name}")


class Cow(Animal):
    species = "cow"
    default_greeting = "Moo!"

    def __init__(self, name, colour="black and white"):
        super().__init__(name, colour)


class Pig(Animal):
    species = "pig"
    default_greeting = "Oink oink!"

    def __init__(self, name, colour="pink"):
        super().__init__(name, colour)


class Horse(Animal):
    species = "horse"
    default_greeting = "Good day to you, sir."

    def __init__(self, name, colour="black"):
        super().__init__(name, colour)


class Habitat:
    def __init__(self, name, max_occupants):
        self.occupants = []
        self._max_occupants = max_occupants

        # I could've just set default names in the child classes, but wanted to play with dunder attributes
        self.name = name if name is not None else self.__class__.__name__.lower()

    @property
    def inventory(self) -> str:
        rem_space_suffix = f"Remaining spaces: {self.remaining_spaces}/{self._max_occupants}"
        if len(self.occupants) == 0:
            return f"{self.name} inventory: Empty. " + rem_space_suffix
        else:
            animal_names = [f"\t\t* {animal.name} the {animal.species}" for animal in self.occupants]
            return (f"{self.name} inventory: {rem_space_suffix}. There's {len(animal_names)} animals in there: \n" +
                    '\n'.join(animal_names))

    @property
    def remaining_spaces(self) -> int:
        return self._max_occupants - len(self.occupants)

    def remove_animal(self, animal):
        if animal in self.occupants:
            self.occupants.remove(animal)
            print(f"Moved {animal.name} the {animal.species} out of the {self.name.lower()}")
        else:
            print(f"Can't remove {animal.name} the {animal.species} because it isn't in the {self.name.lower()}!")

    def add_animal(self, animal):
        # Don't allow exceeding capacity, or trying to add the same animal twice
        if len(self.occupants) < self._max_occupants and animal not in self.occupants:
            self.occupants.append(animal)
            print(f"Moved {animal.name} the {animal.species} to the {self.name.lower()}.")
        else:
            print(f"{animal.name} the {animal.species} can't fit in the {self.name.lower()} because it's full!")

    def move_all(self, destination):
        # Worth caching this since we're using the value several times below
        num_source_occupants = len(self.occupants)

        # Check if source has any animals to move, and if we have enough space in the destination
        if num_source_occupants == 0:
            print(f"Error: move_all operation called on an empty source habitat - the {self.name} is empty.")
        elif destination.remaining_spaces < len(self.occupants):
            print(f"Can't move all {num_source_occupants} animals from the {self.name} to the {destination.name}, "
                  f"because it only has {destination.remaining_spaces} spaces left!")
        else:
            print(f"Moving {num_source_occupants} animals from the {self.name} to the {destination.name}")
            destination.occupants += self.occupants
            self.occupants.clear()


class Barn(Habitat):
    def __init__(self, name="Barn", max_occupants=3):
        super().__init__(name, max_occupants)


class Field(Habitat):
    def __init__(self, name="Field", max_occupants=10):
        super().__init__(name, max_occupants)

from farm import *

barn = Barn(name="Big red barn")
field = Field()

lucy = Cow(name="Lucy", colour="brown")
rob = Pig(name="Rob")
bonnie = Horse(name="Bonnie", colour="white")
rupert = Horse(name="Rupert")

print(lucy)
print(rob)
print(bonnie)
print(rupert)
print()

lucy.speak(sound="MoooooOOOOOOoooo!")
rob.speak()
bonnie.speak()
rupert.speak()
print()

barn.add_animal(lucy)
barn.add_animal(rupert)
field.add_animal(rob)
field.add_animal(bonnie)
print()

print(barn.inventory)
print(field.inventory)
print()

lucy.move(barn, field)
rob.move(barn, field)
print(barn.inventory)
print(field.inventory)
print()

field.move_all(destination=barn)
print(barn.inventory)
print(field.inventory)
print()

barn.move_all(destination=field)
print(barn.inventory)
print(field.inventory)

Lucy is a brown cow.
Rob is a pink pig.
Bonnie is a white horse.
Rupert is a black horse.

Lucy says 'MoooooOOOOOOoooo!'
Rob says 'Oink oink!'
Bonnie says 'Good day to you, sir.'
Rupert says 'Good day to you, sir.'

Moved Lucy the cow to the big red barn.
Moved Rupert the horse to the big red barn.
Moved Rob the pig to the field.
Moved Bonnie the horse to the field.

Big red barn inventory: Remaining spaces: 1/3. There's 2 animals in there: 
        * Lucy the cow
        * Rupert the horse

Field inventory: Remaining spaces: 8/10. There's 2 animals in there: 
        * Rob the pig
        * Bonnie the horse

Moved Lucy the cow out of the big red barn
Moved Lucy the cow to the field.

Error: Can't move Rob from the Big red barn to the Field: animal not present in the Big red barn

Big red barn inventory: Remaining spaces: 2/3. There's 1 animals in there: 
        * Rupert the horse

Field inventory: Remaining spaces: 7/10. There's 3 animals in there: 
        * Rob the pig
        * Bonnie the horse
        * Lucy the cow

Can't move all 3 animals from the Field to the Big red barn, because it only has 2 spaces left!

Big red barn inventory: Remaining spaces: 2/3. There's 1 animals in there: 
        * Rupert the horse

Field inventory: Remaining spaces: 7/10. There's 3 animals in there: 
        * Rob the pig
        * Bonnie the horse
        * Lucy the cow

Moving 1 animals from the Big red barn to the Field

Big red barn inventory: Empty. Remaining spaces: 3/3

Field inventory: Remaining spaces: 6/10. There's 4 animals in there: 
        * Rob the pig
        * Bonnie the horse
        * Lucy the cow
        * Rupert the horse

Field inventory: Remaining spaces: 6/10. There’s 4 animals in there: 
     * Rob the pig 
     * Bonnie the horse 
     * Lucy the cow 
     * Rupert the horse