一天 - 构造者，继承

百变鹏仔 14小时前 #Python

Python中的构造器与继承

Python的构造器是类中名为__init__的特殊方法，在创建对象时自动调用，用于初始化对象属性。如果在__init__方法中未初始化实例变量，则访问这些变量会导致AttributeError错误。

示例：

class Employee:    def __init__(self, name, department, job, year):        self.empname = name  # 初始化实例变量        self.dept = department        self.designation = job        self.joining_year = year    def work(self):        print("Working:", self.empname, self.dept, self.designation, self.joining_year)emp1 = Employee("Guru", "B.Com", "Development", 2025)emp2 = Employee("Pritha", "M.E.", "Design", 2025)emp2.work()

上述代码中，self.empname = name 将参数name赋值给实例变量empname。work()方法打印员工信息。

类属性与实例方法

类属性属于类本身，而实例属性属于特定对象。在实例方法中访问类属性，可以使用self.或.。

class Employee:    salary = 25000  # 类属性    def __init__(self, name, department, job, year):        self.empname = name        self.dept = department        self.designation = job        self.joining_year = year    def work(self):        print("Working:", self.empname, self.dept, self.designation, self.joining_year, self.salary) #访问类属性    def take_leave(self):        print(self.empname)emp1 = Employee("Guru", "B.Com", "Development", 2025)emp2 = Employee("Pritha", "M.E.", "Design", 2025)emp2.work()emp1.take_leave()

__dict__属性

__dict__属性是一个字典，包含对象的属性及其值。

class Employee:    def __init__(self, name, department, job, year):        self.name = name        self.department = department        self.job = job        self.year = yearemp1 = Employee("Guru", "B.Com", "Development", 2025)emp2 = Employee("Pritha", "M.E.", "Design", 2025)print(emp1.__dict__)print(emp2.__dict__)

类方法与装饰器@classmethod

@classmethod装饰器定义与类绑定的方法，而非实例方法。第一个参数是cls，代表类本身。

class Employee:    def __init__(self, name, department, job, year):        self.name = name        self.department = department        self.job = job        self.year = year    @classmethod    def credit_salary(cls):        print("Credit salary on the last day of every month.")Employee.credit_salary() # 调用类方法

内部类

内部类可以访问外部类的属性和方法。

class College:    def __init__(self):        print("College constructor")    class Department:        def __init__(self):            print("Department constructor")        def work(self):            print("Working")principal = College()hod = principal.Department()hod.work()

运算符重载

Python通过特殊方法（如__add__, __mul__等）实现运算符重载。

class Book:    def __init__(self, pages):        self.pages = pages    def __add__(self, other):        return self.pages + other.pagesbook1 = Book(300)book2 = Book(200)print(book1 + book2) # 使用 + 运算符

继承

继承允许类继承其他类的属性和方法。

方法覆盖

子类可以覆盖父类的方法。

class Father:    def work(self):        print("Mechanical Engineer")class Mother:    def work(self):        print("Software Engineer")class Child(Mother, Father): #多继承    def work(self):        print("Business Person")child = Child()child.work() # 调用子类的方法

方法解析顺序 (MRO)

在多继承中，MRO决定方法调用的顺序。 Python 使用 C3线性化算法来确定 MRO。

总而言之，本示例涵盖了Python中的构造器、类属性、实例方法、类方法、内部类、运算符重载以及各种继承类型和方法覆盖，并解释了方法解析顺序。这些概念对于面向对象编程至关重要。

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