Python——封装
2020-12-13 06:05
标签：val 没有 cal odi des isa final error getx 封装指的是将对象的状态信息隐藏在对象内部，不允许外部直接访问对象内部信息，而是通过该类提供的方法来实现对内部信息的操作和访问；封装的含义，实际上，是把该隐藏的隐藏起来，该暴露的暴露出来；Python只需要将类的成员名为以双下划线开头，就可以隐藏类中的成员。 例： 上面例子中，代码print (F.__grade)和print (F.__name)直接访问私有变量会报错setting_grade()、setting_name()方法用于对grade、name进行设置，只有符合条件才能允许设置；print (F._Fraction__grade)和print (F._Fraction__name)通过 _类名来访问对象的实例变量（通常不要这么做），可以看出Python并没有实现真正隐藏，只是改变以双下划线开头的变量，在这些变量前添加单下画线和变量名。 例： 上面代码中，set_usually_score()和set_test_score()用于对usually 、test进行设置；__calculation()是私有方法，默认是隐藏的，只允许内部使用，外部使用会报错，当然也可以使用_类名方法名调用，但并不推荐这么做；print (S.final_grade())通过final_grade()方法内部访问__calculation()私有方法。 先看一下帮助文档： @property 可以在一个类中把方法变成同名属性调用，能用属性的方式来访问该属性。 @x.setter 表示可写，最大作用是用于限制属性的定义，x是被@property修饰的方法名，@x.setter修饰的方法名@property修饰的方法名必须同名。 @x.deleter 表示可删除，x是被@property修饰的方法名，@x.deleter修饰的方法名@property修饰的方法名必须同名。 例： 用property类来实现，例： Python——封装 标签：val 没有 cal odi des isa final error getx 原文地址：https://www.cnblogs.com/qqmb/p/11165556.html一、封装数据属性
class Fraction:
__grade = 0
def __init__(self,name):
self.__name = name
def setting_grade(self,var):
if isinstance(var,int) and var >= 0 and var
=100: Fraction.__grade = var
else:
print (‘请输入正确的分数！‘)
def setting_name(self,set_name):
if isinstance(set_name,str):
self.__name = set_name
else:
print (‘请输入正确的姓名！‘)
def get_fraction(self):
print (‘%s分数是：%s‘%(self.__name,Fraction.__grade))
F = Fraction(‘小黄‘)
print (F.__grade) # 报错 AttributeError: ‘Fraction‘ object has no attribute ‘__grade‘
print (F.__name) # 报错 AttributeError: ‘Fraction‘ object has no attribute ‘__name‘
F.get_fraction() # 打印 小黄分数是：0
F.setting_name(‘小明‘)
F.setting_grade(100) # setting_grade()、setting_name()会对用户设置grade、name进行控制，符合条件才能允许设置
F.get_fraction() # 打印 小明分数是：100
# 可以使用 _类名来访问或修改对象的实例变量print (F._Fraction__grade) # 打印 100
print (F._Fraction__name) # 打印 小明
二、封装函数属性
class SumFraction:
def __init__(self,usually,test):
self.__usually = usually
self.__test = test
def set_usually_score(self,usually_var):
if isinstance(usually_var,int) and usually_var >= 0 and usually_var
=100: self.__usually = usually_var
else:
print (‘请输入正确的分数！‘)
def set_test_score(self,test_var):
if isinstance(test_var,int) and test_var >= 0 and test_var
=100: self.__test = test_var
else:
print (‘请输入正确的分数！‘)
def __calculation(self): # 私有方法，只能内部使用，对外部隐藏运算逻辑
return self.__usually * 0.3 + self.__test * 0.7
def final_grade(self):
return self.__calculation()
S = SumFraction(100,50)
print (S.final_grade()) # 打印 65.0
print (S.__calculation()) # 调用隐藏的__calculation()方法，会报错 AttributeError: ‘SumFraction‘ object has no attribute ‘__calculation‘
print (S._SumFraction__calculation()) # 可以使用_类名方法名调用（不推荐这样做），打印 65.0
# 修改__usually和__testS.set_usually_score(70)
S.set_test_score(100)
print (S.final_grade()) # 通过final_grade()方法内部进行访问__calculation()私有方法，打印 91.0
三、property
>>> help(property)
Help on class property in module builtins:
class property(object)
| property(fget=None, fset=None, fdel=None, doc=None)
|
| Property attribute.
|
| fget
| function to be used for getting an attribute value
| fset
| function to be used for setting an attribute value
| fdel
| function to be used for del‘ing an attribute
| doc
| docstring
|
| Typical use is to define a managed attribute x:
|
| class C(object):
| def getx(self): return self._x
| def setx(self, value): self._x = value
| def delx(self): del self._x
| x = property(getx, setx, delx, "I‘m the ‘x‘ property.")
|
| Decorators make defining new properties or modifying existing ones easy:
|
| class C(object):
| @property
| def x(self):
| "I am the ‘x‘ property."
| return self._x
| @x.setter
| def x(self, value):
| self._x = value
| @x.deleter
| def x(self):
| del self._x
|
| Methods defined here:
|
| __delete__(self, instance, /)
| Delete an attribute of instance.
|
| __get__(self, instance, owner, /)
| Return an attribute of instance, which is of type owner.
|
| __getattribute__(self, name, /)
| Return getattr(self, name).
|
| __init__(self, /, *args, **kwargs)
| Initialize self. See help(type(self)) for accurate signature.
|
| __set__(self, instance, value, /)
| Set an attribute of instance to value.
|
| deleter(...)
| Descriptor to change the deleter on a property.
|
| getter(...)
| Descriptor to change the getter on a property.
|
| setter(...)
| Descriptor to change the setter on a property.
|
| ----------------------------------------------------------------------
| Static methods defined here:
|
| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
|
| ----------------------------------------------------------------------
| Data descriptors defined here:
|
| __isabstractmethod__
|
| fdel
|
| fget
|
| fset
class SumFraction:
def __init__(self,value):
self.__score = value
@property # 读
def score(self):
print (‘读......‘)
return self.__score
@score.setter # 写
def score(self,var):
print (‘写......‘)
if isinstance(var,int) and var >= 0 and var
=100: self.__score = var
return self.__score
else:
print (‘请输入正确的分数！‘)
return
@score.deleter # 删除
def score(self):
print ("删除self.__score......")
del self.__score
S = SumFraction(100)
S.score = 80 # 写，打印 改......
print (S.score)
‘‘‘读，打印读......80‘‘‘del S.score # 删除，打印 删除self.__score......
print (S.score) # __score已被删除，打印 AttributeError: ‘SumFraction‘ object has no attribute ‘_SumFraction__score‘
class SumFraction:
def __init__(self,value):
self.__score = value
def get_score(self):
print (‘读......‘)
return self.__score
def set_score(self,var):
print (‘写......‘)
if isinstance(var,int) and var >= 0 and var
=100: self.__score = var
return self.__score
else:
print (‘请输入正确的分数！‘)
return
def del_score(self):
print ("删除self.__score......")
del self.__score
score = property(get_score,set_score,del_score,‘这里是属性含义~ ‘)
S = SumFraction(100)
S.score = 80 # 写，打印 改......
print (S.score)
‘‘‘读，打印读......80‘‘‘print (SumFraction.score.__doc__) # 属性含义，打印 这里是属性含义~
del S.score # 删除，打印 删除self.__score......
print (S.score) # __score已被删除，打印 AttributeError: ‘SumFraction‘ object has no attribute ‘_SumFraction__score‘