老男孩python学习自修第十八天【面向对象】

1.类与对象（构造方法与实例化）

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class Province:

    def __init__(self, name, capital, leader):
        self.name = name
        self.capital = capital
        self.leader = leader

if __name__ == "__main__":
    hebei = Province("河北", "石家庄", "刘道强")
    print hebei.name
    print hebei.capital
    print hebei.leader

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/Province.py
河北
石家庄
刘道强

Process finished with exit code 0

注意：定义构造方法使用__init__方法

2.动态字段与静态字段

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class Province:

    memo = "中国的23个省之一"

    def __init__(self, name, capital, leader):
        self.name = name
        self.capital = capital
        self.leader = leader

if __name__ == "__main__":
    hebei = Province("河北", "石家庄", "刘道强")
    print hebei.name
    print hebei.capital
    print hebei.leader

    print hebei.memo
    print Province.memo

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/Province.py
河北
石家庄
刘道强
中国的23个省之一
中国的23个省之一

Process finished with exit code 0

注意：

（1）类不能访问动态字段

（2）对象可以访问静态字段

3.动态方法与静态方法

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class Province:

    memo = "中国的23个省之一"

    def __init__(self, name, capital, leader):
        self.name = name
        self.capital = capital
        self.leader = leader

    def sports_meeting(self):
        return self.name + "正在开运动会"

    @staticmethod
    def foo():
        return "每个省都在反腐"

if __name__ == "__main__":
    hebei = Province("河北", "石家庄", "刘道强")
    print hebei.name
    print hebei.capital
    print hebei.leader

    print hebei.memo
    print Province.memo

    print hebei.sports_meeting()
    print hebei.foo()
    print Province.foo()

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/Province.py
河北
石家庄
刘道强
中国的23个省之一
中国的23个省之一
河北正在开运动会
每个省都在反腐
每个省都在反腐

Process finished with exit code 0

注意：

（1）类不能访问动态方法

（2）对象可以方位静态方法

（3）在动态方法上增加@staticmethod并去除self参数则为动态方法

4.特性

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class Province:

    memo = "中国的23个省之一"

    def __init__(self, name, capital, leader):
        self.name = name
        self.capital = capital
        self.leader = leader

    def sports_meeting(self):
        return self.name + "正在开运动会"

    @staticmethod
    def foo():
        return "每个省都在反腐"

    @property
    def bar(self):
        return self.name

if __name__ == "__main__":
    hebei = Province("河北", "石家庄", "刘道强")
    print hebei.name
    print hebei.capital
    print hebei.leader

    print hebei.memo
    print Province.memo

    print hebei.sports_meeting()
    print hebei.foo()
    print Province.foo()

    print hebei.bar

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/Province.py
河北
石家庄
刘道强
中国的23个省之一
中国的23个省之一
河北正在开运动会
每个省都在反腐
每个省都在反腐
河北

Process finished with exit code 0

注意：

（1）在方法上增加@property则该方法变为字段访问

5.面向对象中动态方法与静态方法的比较

（1）使用动态方法适合于业务类；适用于对象数量较少的情况

（2）使用静态方法适合于工具类；适用于对象数量较多的情况，当对象较多则创建对象占用大量的内存这时应该使用静态方法

6.私有字段与私有方法

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class Province:

    memo = "中国的23个省之一"

    def __init__(self, name, capital, leader, __thailand):
        self.name = name
        self.capital = capital
        self.leader = leader
        self.__thailand = __thailand

    def sports_meeting(self):
        return self.name + "正在开运动会"

    @staticmethod
    def foo():
        return "每个省都在反腐"

    @property
    def bar(self):
        return self.name

    @property
    def thailand(self):
        return self.__thailand

if __name__ == "__main__":
    hebei = Province("河北", "石家庄", "刘道强", True)
    print hebei.name
    print hebei.capital
    print hebei.leader

    print hebei.memo
    print Province.memo

    print hebei.sports_meeting()
    print hebei.foo()
    print Province.foo()

    print hebei.bar

    print hebei.thailand

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/Province.py
河北
石家庄
刘道强
中国的23个省之一
中国的23个省之一
河北正在开运动会
每个省都在反腐
每个省都在反腐
河北
True

Process finished with exit code 0

注意：

（1）任何暴露给外部是无用的，或者为了安全不能暴露给外部的字段和方法需要设置为私有；设置私有字段和私有方法只需在前边加上两个下划线即可

（2）私有字段在类内部可以直接访问，在类外部不能访问，可以通过实现特性来访问私有字段

（3）私有方法在类内部可以直接访问，在类外部不能访问，可以通过封装共有方法来访问私有方法

7.只读特性与可写特性

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class Province:

    memo = "中国的23个省之一"

    def __init__(self, name, capital, leader, __thailand):
        self.name = name
        self.capital = capital
        self.leader = leader
        self.__thailand = __thailand

    def sports_meeting(self):
        return self.name + "正在开运动会"

    @staticmethod
    def foo():
        return "每个省都在反腐"

    @property
    def bar(self):
        return self.name

    @property
    def thailand(self):
        return self.__thailand

    @thailand.setter
    def thailand(self, __thailand):
        self.__thailand = __thailand

if __name__ == "__main__":
    hebei = Province("河北", "石家庄", "刘道强", True)
    print hebei.name
    print hebei.capital
    print hebei.leader

    print hebei.memo
    print Province.memo

    print hebei.sports_meeting()
    print hebei.foo()
    print Province.foo()

    print hebei.bar

    print hebei.thailand
    hebei.thailand = False
    print hebei.thailand

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/Province.py
河北
石家庄
刘道强
中国的23个省之一
中国的23个省之一
河北正在开运动会
每个省都在反腐
每个省都在反腐
河北
True
False

Process finished with exit code 0

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/Province.py
河北
石家庄
刘道强
中国的23个省之一
中国的23个省之一
河北正在开运动会
每个省都在反腐
每个省都在反腐
河北
True
False

Process finished with exit code 0

注意

（1）使用@property装饰器则私有字段可读；使用@field.setter则私有字段可写

8.构造方法__init__()，析构方法__del__()和__call__()

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class Province:

    memo = "中国的23个省之一"

    def __init__(self, name, capital, leader, __thailand):
        self.name = name
        self.capital = capital
        self.leader = leader
        self.__thailand = __thailand

    def __call__(self, *args, **kwargs):
        print "CALL"

    def __del__(self):
        print "DELETE"

    def sports_meeting(self):
        return self.name + "正在开运动会"

    @staticmethod
    def foo():
        return "每个省都在反腐"

    @property
    def bar(self):
        return self.name

    @property
    def thailand(self):
        return self.__thailand

    @thailand.setter
    def thailand(self, __thailand):
        self.__thailand = __thailand

if __name__ == "__main__":
    hebei = Province("河北", "石家庄", "刘道强", True)
    print hebei.name
    print hebei.capital
    print hebei.leader

    print hebei.memo
    print Province.memo

    print hebei.sports_meeting()
    print hebei.foo()
    print Province.foo()

    print hebei.bar

    print hebei.thailand
    hebei.thailand = False
    print hebei.thailand

    hebei()

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/Province.py
河北
石家庄
刘道强
中国的23个省之一
中国的23个省之一
河北正在开运动会
每个省都在反腐
每个省都在反腐
河北
True
False
CALL
DELETE

Process finished with exit code 0

注意：

__init__(self)在创建对象的时候触发调用

__del__(self)在销毁对象的时候触发调用

__call__(self)在对象()调用时触发调用

9.类的继承

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class Base:

    def __int__(self):
        pass

    def __call__(self, *args, **kwargs):
        pass

    def __del__(self):
        pass

    def foo(self):
        print "foo"

    def bar(self):
        print "bar"

class Derive(Base):
    def __int__(self):
        pass

    def __call__(self, *args, **kwargs):
        pass

    def __del__(self):
        pass

    def bar(self):
        Base.bar(self)
        print "derive"

if __name__ == "__main__":
    base = Base()
    base.foo()
    base.bar()

    derive = Derive()
    derive.foo()
    derive.bar()

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/extend_test.py
foo
bar
foo
bar
derive

Process finished with exit code 0

注意：

（1）继承只需要的类名的后面加上基类的名称

（2）调用基类的方法则用Base.bar(self)

10. 多继承

经典类的深度优先多继承：

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class A:
    def __init__(self):
        print "init A"

    def save(self):
        print "save from A"

class B(A):
    def __init__(self):
        print "init B"

class C(A):
    def __init__(self):
        print "init C"

    def save(self):
        print "save from C"

class D(B, C):
    def __init__(self):
        print "init D"

if __name__ == "__main__":
    d = D()
    d.save()

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/object_test.py
init D
save from A

Process finished with exit code 0

新式类的广度优先多继承：

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

class A(object):
    def __init__(self):
        print "init A"

    def save(self):
        print "save from A"

class B(A):
    def __init__(self):
        print "init B"

class C(A):
    def __init__(self):
        print "init C"

    def save(self):
        print "save from C"

class D(B, C):
    def __init__(self):
        print "init D"

if __name__ == "__main__":
    d = D()
    d.save()

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/object_test.py
init D
save from C

Process finished with exit code 0

注意：

（1）python中的类如果不继承object则为经典类，如果继承object类则为新式类

（2）经典类的多继承采用深度优先算法继承，新式类的多继承采用广度优先算法继承

11.接口，抽象类，抽象方法

例如：

#!/usr/bin/env python
# _*_ coding:UTF-8 _*_

from abc import ABCMeta, abstractmethod

class Foo:

    __metaclass__ = ABCMeta

    def save(self):
        pass

class Bar(Foo):
    def __init__(self):
        print "init Bar"

    def save(self):
        print "save from Bar"

if __name__ == "__main__":
    bar = Bar()
    bar.save()

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day05/day18/abstract_test.py
init Bar
save from Bar

Process finished with exit code 0

注意：

（1）抽象类中只有抽象方法即为借口

（2）类中有__metaclass__ = ABCMeta的类即为抽象类；方法被@abstractmethod装饰即为抽象方法