4.8. Polymorphism

4.8.1. Switch

Listing 4.35. Switch moves business logic to the execution place

watney = 'Astronaut'

if watney == 'Astronaut':
    print('Hello')
elif watney == 'Cosmonaut':
    print('Привет!')
elif watney == 'Taikonaut':
    print('你好')
else:
    print('Default Value')

# Hello

def say_hello(key=None):
    return {
        'Astronaut': 'Hello',
        'Cosmonaut': 'Привет!',
        'Taikonaut': '你好',
    }.get(key, 'Default Value')


watney = 'Astronaut'
ivanovic = 'Cosmonaut'
twardowski = 'Sorcerer'

say_hello(watney)
# Hello

say_hello(ivanovic)
# Привет!

say_hello(twardowski):
# 'Default Value'

4.8.2. Polymorphism in a Function

Listing 4.36. Polymorphism on Function

class Sorcerer:
    pass

class Astronaut:
    def say_hello(self):
        return 'Hello'

class Cosmonaut:
    def say_hello(self):
        return 'Привет!'


def say_hello(spaceman):
    if hasattr(spaceman, 'say_hello')
        return spaceman.say_hello()
    else:
        return 'Default Value'


watney = Astronaut()
ivanovic = Cosmonaut()
twardowski = Sorcerer()

say_hello(watney)
# Hello

say_hello(ivanovic)
# Привет!

say_hello(twardowski)
# 'Default Value'

4.8.3. Polymorphism on a Class

Listing 4.37. Polymorphism on Classes

class Astronaut:
    def __init__(self, name):
        self.name = name

    def say_hello(self):
        return 'Hello'


class Cosmonaut:
    def __init__(self, name):
        self.name = name

    def say_hello(self):
        return 'Привет!'


crew = [
    Astronaut('Mark Watney'),
    Cosmonaut('Иван Иванович'),
    Astronaut('Matt Kowalski'),
    Cosmonaut('Jan Twardowski'),
]

for member in crew:
    print(member.say_hello())
# Hello
# Привет!
# Hello
# Привет!