python学习之继承
面向对象编程 (OOP) 语言的一个主要功能就是“继承”。继承是指这样一种能力：它可以使用现有类的所有功能，并在无需重新编写原来的类的情况下对这些功能进行扩展。
通过继承创建的新类称为“子类”或“派生类”。
被继承的类称为“基类”、“父类”或“超类”。
继承的过程，就是从一般到特殊的过程。
要实现继承，可以通过“继承”（Inheritance）和“组合”（Composition）来实现。
在某些 OOP 语言中，一个子类可以继承多个基类。但是一般情况下，一个子类只能有一个基类，要实现多重继承，可以通过多级继承来实现。
继承概念的实现方式主要有2类：实现继承、接口继承。
1）实现继承是指使用基类的属性和方法而无需额外编码的能力；
2）接口继承是指仅使用属性和方法的名称、但是子类必须提供实现的能力(子类重构爹类方法)；
在考虑使用继承时，有一点需要注意，那就是两个类之间的关系应该是“属于”关系。例如，Employee 是一个人，Manager 也是一个人，因此这两个类都可以继承 Person 类。但是 Leg 类却不能继承 Person 类，因为腿并不是一个人。
抽象类仅定义将由子类创建的一般属性和方法。
OO开发范式大致为：划分对象→抽象类→将类组织成为层次化结构(继承和合成) →用类与实例进行设计和实现几个阶段。
继承示例
| #!/usr/bin/env python #coding: utf8 class SchoolMember(object): members = 0 # 初始学校人数为0 def __init__(self, name, age): self.name = name self.age = age def tell(self): pass def enroll(self): '''注册''' SchoolMember.members += 1 print( "\033[32;1mnew member [%s] is enrolled,now there are [%s] members.\033[0m " % (self.name, SchoolMember.members)) def __del__(self): '''析构方法''' print("\033[31;1mmember [%s] is dead!\033[0m" % self.name) class Teacher(SchoolMember): def __init__(self, name, age, course, salary): super(Teacher, self).__init__(name, age) self.course = course self.salary = salary self.enroll() def teaching(self): '''讲课方法''' print("Teacher [%s] is teaching [%s] for class [%s]" % (self.name, self.course, 's1')) def tell(self): '''自我介绍方法''' msg = '''Hi, my name is [%s], works for [%s] as a [%s] teacher !''' % (self.name, 'IT trainning', self.course) print(msg) class Student(SchoolMember): def __init__(self, name, age, grade, sid): super(Student, self).__init__(name, age) self.grade = grade self.sid = sid self.enroll() def tell(self): '''自我介绍方法''' msg = '''Hi, my name is [%s], I'm studying [%s] in [%s]!''' % (self.name, self.grade, 'IT trainning') print(msg) if __name__ == '__main__': t1 = Teacher("peng", 22, 'Python', 20000) t2 = Teacher("lisi", 29, 'Linux', 3000) s1 = Student("xiaowang", 24, "Python S1", 1483) s2 = Student("xiaoming", 26, "Python S1", 1484) t1.teaching() t2.teaching() t1.tell() |
脚本执行结果如下：
new member [peng] is enrolled,now there are [1] members.
new member [lisi] is enrolled,now there are [2] members.
new member [xiaowang] is enrolled,now there are [3] members.
new member [xiaoming] is enrolled,now there are [4] members.
Teacher [peng] is teaching [Python] for class [s1]
Teacher [lisi] is teaching [Linux] for class [s1]
Hi, my name is [peng], works for [IT trainning] as a [Python] teacher !
member [lisi] is dead!
member [xiaoming] is dead!
member [peng] is dead!
member [xiaowang] is dead!
