python类 | 北鱼IT

文章索引

1. 类（Class）

类是对象的蓝图或模板。它定义了对象的属性和方法。

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def bark(self):
        print(f"{self.name} is barking.")

class Dog:

def __init__(self, name, age):

self.name = name

self.age = age

def bark(self):

print(f"{self.name} is barking.")

2. 对象（Object）

对象是类的实例。它是类的具体实现。

my_dog = Dog("Buddy", 3)
print(f"My dog's name is {my_dog.name}.")  # 输出: My dog's name is Buddy.
my_dog.bark()  # 输出: Buddy is barking.

my_dog = Dog("Buddy", 3)

print(f"My dog's name is {my_dog.name}.") # 输出: My dog's name is Buddy.

my_dog.bark() # 输出: Buddy is barking.

3. 属性（Attribute）

属性是对象的状态或数据。

class Car:
    def __init__(self, brand, model):
        self.brand = brand
        self.model = model

my_car = Car("Toyota", "Corolla")
print(f"My car is a {my_car.brand} {my_car.model}.")  # 输出: My car is a Toyota Corolla.

class Car:

def __init__(self, brand, model):

self.brand = brand

self.model = model

my_car = Car("Toyota", "Corolla")

print(f"My car is a {my_car.brand} {my_car.model}.") # 输出: My car is a Toyota Corolla.

4. 方法（Method）

方法是定义在类中的函数，用来描述对象的行为。

class Circle:
    def __init__(self, radius):
        self.radius = radius

    def get_area(self):
        return 3.14 * self.radius ** 2

my_circle = Circle(5)
print(f"Area of the circle: {my_circle.get_area()}")  # 输出: Area of the circle: 78.5

class Circle:

def __init__(self, radius):

self.radius = radius

def get_area(self):

return 3.14 * self.radius ** 2

my_circle = Circle(5)

print(f"Area of the circle: {my_circle.get_area()}") # 输出: Area of the circle: 78.5

5. 继承（Inheritance）

继承允许一个类继承另一个类的属性和方法。

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

    def make_sound(self):
        print(f"{self.name} makes a sound.")

class Cat(Animal):
    def make_sound(self):
        print(f"{self.name} meows.")

my_cat = Cat("Whiskers")
my_cat.make_sound()  # 输出: Whiskers meows.

class Animal:

def __init__(self, name):

self.name = name

def make_sound(self):

print(f"{self.name} makes a sound.")

class Cat(Animal):

def make_sound(self):

print(f"{self.name} meows.")

my_cat = Cat("Whiskers")

my_cat.make_sound() # 输出: Whiskers meows.

6. 封装（Encapsulation）

封装是将数据和方法结合在一起，并对数据进行保护，不让外部直接访问。

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance

    def deposit(self, amount):
        self.__balance += amount

    def get_balance(self):
        return self.__balance

account = BankAccount(100)
account.deposit(50)
print(f"Balance: {account.get_balance()}")  # 输出: Balance: 150
# print(account.__balance)  # 这行代码会报错，因为 __balance 是私有的

class BankAccount:

def __init__(self, balance):

self.__balance = balance

def deposit(self, amount):

self.__balance += amount

def get_balance(self):

return self.__balance

account = BankAccount(100)

account.deposit(50)

print(f"Balance: {account.get_balance()}") # 输出: Balance: 150

# print(account.__balance) # 这行代码会报错，因为 __balance 是私有的

7. 多态（Polymorphism）

多态允许不同的类以相同的接口来实现不同的功能。

class Bird:
    def fly(self):
        print("Bird is flying.")

class Airplane:
    def fly(self):
        print("Airplane is flying.")

def make_it_fly(flying_object):
    flying_object.fly()

bird = Bird()
airplane = Airplane()

make_it_fly(bird)  # 输出: Bird is flying.
make_it_fly(airplane)  # 输出: Airplane is flying.

class Bird:

def fly(self):

print("Bird is flying.")

class Airplane:

def fly(self):

print("Airplane is flying.")

def make_it_fly(flying_object):

flying_object.fly()

bird = Bird()

airplane = Airplane()

make_it_fly(bird) # 输出: Bird is flying.

make_it_fly(airplane) # 输出: Airplane is flying.