OOP python

• 参考：https://realpython.com/python3-object-oriented-programming/#what-is-object-oriented-programming-oop

what’s OOP

• Definition: is a programming paradigm which provides a means of structuring programs so that properties and behaviors are bundled into individual objects.
• 类似于一个人有名字、年龄、地址等属性

Classes in python

• Definition: classes are used to create user-defined data structures that contain arbitrary information about something.

Python Objects(instances)

• 实例

How to define a class in Python

Instance Attributes

• self是用来记录每一个类的实例

class Dog:

    # Class Attribute
    species = 'mammal'

    # Initializer / Instance Attributes
    def __init__(self, name, age):
        self.name = name
        self.age = age

作业：Using the same Dog class, instantiate three new dogs, each with a different age. Then write a function called, get_biggest_number(), that takes any number of ages (*args) and returns the oldest one. Then output the age of the oldest dog like so:
The oldest dog is 7 years old.

class Dog:

    # Class Attribute
    species = 'mammal'

    # Initializer / Instance Attributes
    def __init__(self, name, age):
        self.name = name
        self.age = age


# Instantiate the Dog object
jake = Dog("Jake", 7)
doug = Dog("Doug", 4)
william = Dog("William", 5)


# Determine the oldest dog
def get_biggest_number(*args):
    return max(args)

Instance Methods

• 用来获取实例内容

class Dog:

    # Class Attribute
    species = 'mammal'

    # Initializer / Instance Attributes
    def __init__(self, name, age):
        self.name = name
        self.age = age

    # instance method
    def description(self):
        return "{} is {} years old".format(self.name, self.age)

    # instance method
    def speak(self, sound):
        return "{} says {}".format(self.name, sound)
        
# Instantiate the Dog object
mikey = Dog("Mikey", 6)

# call our instance methods
print(mikey.description())
print(mikey.speak("Gruff Gruff"))

调整属性

>>> class Email:
...     def __init__(self):
...         self.is_sent = False
...     def send_email(self):
...         self.is_sent = True
...
>>> my_email = Email()
>>> my_email.is_sent
False
>>> my_email.send_email()
>>> my_email.is_sent
True

Python Object Inheritance

# Parent class
class Dog:

    # Class attribute
    species = 'mammal'

    # Initializer / Instance attributes
    def __init__(self, name, age):
        self.name = name
        self.age = age

    # instance method
    def description(self):
        return "{} is {} years old".format(self.name, self.age)

    # instance method
    def speak(self, sound):
        return "{} says {}".format(self.name, sound)


# Child class (inherits from Dog class)
class RussellTerrier(Dog):
    def run(self, speed):
        return "{} runs {}".format(self.name, speed)


# Child class (inherits from Dog class)
class Bulldog(Dog): # 继承
    def run(self, speed):
        return "{} runs {}".format(self.name, speed)


# Child classes inherit attributes and
# behaviors from the parent class
jim = Bulldog("Jim", 12)
print(jim.description())

# Child classes have specific attributes
# and behaviors as well
print(jim.run("slowly"))