[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

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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