[Python基础]005.语法(4)

语法(4)

---

• 类
  • 创建
  • self
  • 方法
  • 变量
  • 综合例子
• 继承

类

创建

• 与其他大部分语言一样，Python也用 class 来创建类。

    class Person:       # Person类
        pass            # 空语句

• 创建实例

    person = Person()   # 创建Person实例
    print person        # 会打印出实例信息

self

• Python中使用 self 来指代实例自己，相当于Java、C++中的 this
• Python中类的每个成员方法的第一个参数必须是 self，这样类中每个方法就都可以调用到实例自己。

方法

• 成员方法： 以self作为第一个参数

    class Person:
  
        def sleep(self, t):         # 定义成员方法
            print 'sleep %f' % t
            print self              # 实例信息
  
    Person().sleep()

• 构造方法： __init__是Python类的构造方法。

    class Person:
  
        def __init__(self, name, age):      # 构造方法
            print name
            print age
            pass

  创建实例时写入参数

    person = Person('AC', 30)

  也可以像普通方法一样，定义默认参数

    class Person:
        def __init__(self, name, age=10):
            print name
            print aeg
            pass
  
    person = Person('AC')

• 类方法： 静态方法，相当于Java与C++里的static方法
  只要不写self变量，方法就是静态方法，还需要加上@staticmethod来修饰。

    class Person:
  
        @staticmethod       # 方法修饰
        def count():        # 类方法
            return 0
  
    print Person.count() 

变量

• 类变量： 静态变量，相当于static
  调用时用 类名.变量名

    class Person:
        num = 0                 # 定义类变量num
  
        @staticmethod
        def count():
            return Person.num   # 类方法调用
  
    print Person.num            # 调用
    print Person.count()

• 成员变量： 定义和调用时都直接用 self.变量名

    class Person:
  
        def __init__(self, name, age):
            self.name = name            # 创建name属性，并赋值
            self.age = age              # 创建age属性，并赋值
  
        def info(self):
            print self.name             # 调用
            print self.age

综合例子

# Person.py

class Person:

    num = 0     # 总人数

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

        Person.num = Person.num + 1     # 每创建一个实例，总人数加1

    @staticmethod
    def count():
        """
        获得总人数
        """
        return Person.num

    def info(self):
        """
        打印信息
        """
        print self.name
        print self.age

p1 = Person('AC', 30)
p2 = Person('Mount', 18)

p1.age = 31         # 修改变量

print p1.info()
print p2.info()
print Person.count()

继承

• 在定义类时，在类名后加上(父类)。

    # Programmer.py
  
    from Person import Person
  
    class Programmer(Person):
        pass

  这样Programmer就继承了Person。

• 没有继承的类与Java一样都默认继承自一个继承类 object
  相当于

    class Person(object):
        pass

• 方法重写

    # Programmer.py
  
    from Person import Person
  
    class Programmer(Person):
  
        def __init__(self, name, age, lang):     # 重写构造方法
  
            Person.__init__(self, name, age)     # 调用父类构造方法
  
            self.lang = lang                      # 添加的语言属性
  
        def info(self):                           # 重写父类方法
            print 'Programmer'
            print self.name
            print self.age
  
    Programmer('AC', 30, 'lua').info()
    print Person.couont()

  除了重写的方法，Programmer类会继承Person类的一切。

• 没有继承的类与Java一样都默认继承自一个继承类 object
  相当于

    class Person(object):
        pass

• Python支持多重继承

    class A:
        pass
    class B:
        pass
    class C:
        pass
  
    class Person(A, B, C):          # 继承多个类
        pass

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本站文章为宝宝巴士 SD.Team原创，转载务必在明显处注明：（作者官方网站：宝宝巴士) 
转载自【宝宝巴士SuperDo团队】 原文链接: http://www.cnblogs.com/superdo/p/4528963.html

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