2018-12-04

作者: Karl_2c80 | 来源:发表于2018-12-04 22:57 被阅读0次

类和对象

类是对事物的抽象，对象是类的一个实例
面向对象的主要思想：
1. 封装
2. 继承
3. 多态

类定义

类把需要的变量和函数组合到一起，这种包含称为“封装 ”
class A(object):
类的结构：
- 成员变量 - 属性
- 成员函数 - 方法

类的属性

类的属性分为公有属性和私有属性
以双下划线开头的为私有属性，如__atrr
公有属性在类中和类外都能调用
私有属性不能在类外调用
在类外可通过 instance._classname__attribute 方式访问私有属性，一般用作测试
内置属性：由系统在定义类时默认添加的，有前后双下划线构成

类的方法

类的方法和普通函数的最大区别在于：至少有一个参数self
类的方法有如下几种：
1. 公有方法：在类中和类外都能调用
2. 私有方法：不能在类外调用，以双下划线开头 __func()
3. 类方法：被classmethod()函数处理过的方法，除能被对象调用外，也能被类调用
4. 静态方法：被staticmethod()函数处理过的方法，相当于“全局函数”，可被类直接调用，也可被所有实例化对象所调用，静态方法没有self参数

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

me = MyClass()
print me.id
me.think()

[root@KARL ~]# python u3.py
7
My name is Karl
My age is 28

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

me = MyClass()
print me.id
me.think()
# print me.__age        ## 在类外无法直接调用类中的私有属性
print '*'*20
print me._MyClass__age          ## 不推荐这样使用，一般用作测试

[root@KARL ~]# python u3.py
7
My name is Karl
My age is 28
********************
28

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

me = MyClass()
#me.think()
print '*'*20
print me.__dict__

[root@KARL ~]# python u3.py
********************
{}

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

me = MyClass()
me.think()
print me.name
print me.id
print '*'*20
print me.__dict__

[root@KARL ~]# python u3.py
My name is Karl
My age is 28
Karl
7
********************
{'_MyClass__age': 28}

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        name = 'John'
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

me = MyClass()
print '*'*20
print MyClass.name      # 直接通过类获取类的属性

[root@KARL ~]# python u3.py
********************
Karl

▽
#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        name = 'John'
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

me = MyClass()
me.id = 123
print '*'*20
print MyClass.name      # 直接通过类获取类的属性
print MyClass.id
print me.id

[root@KARL ~]# python u3.py
********************
Karl
7
123

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        name = 'John'
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

me = MyClass()
me.id = 123
print '*'*20
print MyClass.name      # 直接通过类获取类的属性
print MyClass.id
print me.id
print '#'*20
print MyClass.__dict__

[root@KARL ~]# python u3.py
********************
Karl
7
123
####################
{'__module__': '__main__', 'name': 'Karl', 'think': <function think at 0x7fc9aec715f0>, '_MyClass__age': 18, '__doc__': None, '__dict__': <attribute '__dict__' of 'MyClass' objects>, '__weakref__': <attribute '__weakref__' of 'MyClass' objects>, 'id': 7}

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        name = 'John'
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

    def __secret(self):
        print "I can tell you a secret!"

    def tell(self):
        self.__secret()

    cm = classmethod(tell)   # classmethod不能处理私有方法

me = MyClass()
print '*'*20
me.tell()
print '#'*20
MyClass.cm()

[root@KARL ~]# python u3.py
********************
I can tell you a secret!
####################
Traceback (most recent call last):
  File "u3.py", line 27, in <module>
    MyClass.cm()
  File "u3.py", line 19, in tell
    self.__secret()
TypeError: unbound method __secret() must be called with MyClass instance as first argument (got nothing instead)

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        name = 'John'
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

    def __secret(self):
        print "I can tell you a secret!"

    def tell(self):
        self.__secret()

    cm = classmethod(think)

me = MyClass()
print '*'*20
me.tell()
print '#'*20
MyClass.cm()

[root@KARL ~]# python u3.py
********************
I can tell you a secret!
####################
My name is Karl
My age is 28

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        name = 'John'
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

    def __secret(self):
        print "I can tell you a secret!"

    def tell(self):
        self.__secret()

    def test():                 # 注意没带参数self
        print "This is a static func"

    cm = classmethod(think)     # 类方法

    sm = staticmethod(test)     # 静态方法

me = MyClass()
print '*'*20
me.tell()
print '#'*20
MyClass.sm()

[root@KARL ~]# python u3.py
********************
I can tell you a secret!
####################
This is a static func

以下两种代码效果相同

# 1) 通过类名调用类方法和静态方法
#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        name = 'John'
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

    def __secret(self):
        print "I can tell you a secret!"

    def tell(self):
        self.__secret()

    def test():                 # 注意没带参数self
        print "This is a static func"

    def test2(self):
        print "This is a class func"

    cm = classmethod(test2)     # 类方法

    sm = staticmethod(test)     # 静态方法

me = MyClass()
print '*'*20
MyClass.cm()
print '#'*20
MyClass.sm()

# 1) 结果显示：
[root@KARL ~]# python u3.py
********************
This is a class func
####################
This is a static func

# 2) 通过装饰器实现相同效果
#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        name = 'John'
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

    def __secret(self):
        print "I can tell you a secret!"

    def tell(self):
        self.__secret()

    @staticmethod
    def test():                 # 注意没带参数self
        print "This is a static func"

    @classmethod
    def test2(self):
        print "This is a class func"

#    cm = classmethod(test2)    # 类方法

#    sm = staticmethod(test)    # 静态方法

me = MyClass()
print '*'*20
MyClass.test2()
print '#'*20
MyClass.test()

# 2) 结果显示：
[root@KARL ~]# python u3.py
********************
This is a class func
####################
This is a static func

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2018-12-04

类和对象

类定义

类的属性

类的方法

以下两种代码效果相同

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