python封装及意义

这种变形的特点:
1,在类外部无法直接obj.__AttrName
2,在类内部可以直接使用:obj.__AttrName
3,子类无法覆盖父类__开头的属性

0,

class A:
    '类的封装啊'
    __x = 1    #  _A__x = 1
    print('你去吃啥饭0000')
    def __init__(self,name):
        print('执行__init__')
        self.__name = name     #   self._A__name = name

    def __foo(self):   #  def _A__foo
        print('run foo')
        print('你去吃啥饭__foo')

    def bar(self):
        print('你去吃啥饭bar')
        self.__foo()
        print('from Bar')

print(A.__dict__)

a = A('egon')
# print(A._A__foo(a))
# a._A__foo()
# a.bar()
print(a._A__name)
# print(a.__name)
# # a._A__foo()
print('隐藏了呢',a._A__x)

输出:

你去吃啥饭0000
{'__module__': '__main__', '__doc__': '类的封装啊', '_A__x': 1, '__init__': <function A.__init__ at 0x000001BD2399D0D0>, '_A__foo': <function A.__foo at 0x000001BD2399D158>, 'bar': <function A.bar at 0x000001BD2399D1E0>, '__dict__': <attribute '__dict__' of 'A' objects>, '__weakref__': <attribute '__weakref__' of 'A' objects>}
执行__init__
egon
隐藏了呢 1

1,

class Foo:
    def __func(self):   #   _Foo__func
        print('from foo')

class Bar(Foo):
    def __func(self):   #   _Bar__func
        print('from bar')

b = Bar()
b._Bar__func()
b._Foo__func()

输出:

from bar
from foo

2,

class B:
    __x = 1
    def __init__(self,name):   #   _Bar__func
        self.__name = name   #   self._B__name = name
    def pirnt(self):
        print('你好啊',self.__z)

print(B._B__x)
B.__y = 2
print(B.__dict__)

b = B('egon')

print(b.__dict__)

b.__age = 18
print(b.__dict__)
print(b.__age)
B._B__z = 2
# B.pirnt(b)
b.pirnt()
print(B.__dict__)

输出:

1
{'__module__': '__main__', '_B__x': 1, '__init__': <function B.__init__ at 0x000002B30320D0D0>, 'pirnt': <function B.pirnt at 0x000002B30320D158>, '__dict__': <attribute '__dict__' of 'B' objects>, '__weakref__': <attribute '__weakref__' of 'B' objects>, '__doc__': None, '__y': 2}
{'_B__name': 'egon'}
{'_B__name': 'egon', '__age': 18}
18
你好啊 2
{'__module__': '__main__', '_B__x': 1, '__init__': <function B.__init__ at 0x000002B30320D0D0>, 'pirnt': <function B.pirnt at 0x000002B30320D158>, '__dict__': <attribute '__dict__' of 'B' objects>, '__weakref__': <attribute '__weakref__' of 'B' objects>, '__doc__': None, '__y': 2, '_B__z': 2}

3 封装执行顺序

class A:
    def foo(self):
        print('A.foo')

    def bar(self):
        print('A.bar')
        self.foo()   #b.foo()

class B(A):
    def foo(self):
        print('B.foo')

b = B()
b.bar()

print('-----------------------------------------------------------')

class A:
    def __foo(self):   #   _A__foo
        print('A.foo')

    def bar(self):
        print('A.bar')
        self.__foo()   #   self._A.foo()

class B(A):
    def __foo(self):   #   _B__foo
        print('B.foo')

b = B()
b.bar()

输出:

A.bar
B.foo
-----------------------------------------------------------
A.bar
A.foo

封装的意义

 #_*_ encoding: utf-8 _*_   @author: ty  hery   2018/12/14
#   1,封装数据属性: 明确区分内外,控制外部对隐藏属性的操作行为
class People:
    def __init__(self,name,age):
        self.__name = name     #   self._A__name = name
        self.__age = age     #   self._A__name = name

    def tell_info(self):   #def _A__foo
        print('Name:<%s> Age:<%s>' %(self.__name,self.__age))

    def set_info(self,name,age):   #def _A__foo
        if not isinstance(name,str):
            print('名字必须是字符串类型')
            return
        if not isinstance(age,int):
            print('年龄必须是数字类型')
            return
        self.__name = name
        self.__age = age

p = People('egon',19)
p.tell_info()
print(p.__dict__)
print(p._People__age)
p.set_info('55',39)
print(p.__dict__)


# 封装方法:隔离复杂度
class ATM:
    def __card(self):
        print('插卡')
    def __auth(self):
        print('用户认证')
    def __input(self):
        print('输入取款金额')
    def __print_bill(self):
        print('打印账单')
    def __take_money(self):
        print('取款')

    def withdraw(self):
        self.__card()
        self.__auth()
        self.__input()
        self.__print_bill()
        self.__take_money()
a=ATM()
a.withdraw()

输出:

Name:<egon> Age:<19>
{'_People__name': 'egon', '_People__age': 19}
19
{'_People__name': '55', '_People__age': 39}
插卡
用户认证
输入取款金额
打印账单
取款