Introduction python properties and its application in property

Python functional property is the property: property attributes series of internal logic calculation, the results will eventually return.
Using property modified instance method is called, it can be the same as the instance properties

property usage 1-- decorator way

Application @property decorator instance method on a class

class Test:
    def __init__(self):
        self.__num = 100

    @property
    def num(self):
        print("--get--")
        return self.__num

    @num.setter
    def num(self, num):
        print("--set--")
        self.__num = num

t = Test()
print(t.num)
t.num = 1
"""
--get--
100
--set--
"""

Define and call property the property should pay attention to the following points:

• Defining added @property decorator on the basis of the example of the method; and only a self parameter.
• When you call, you do not need parentheses.
• Classic properties in only one access method, which corresponds to the modified method @property.
• The new class attributes, there are three access methods, and are respectively corresponding to the three @ property, @ method name .setter, @ .deleter method for modifying the method name.

• Classes in Python classic classes and new classes, new classes of property than the rich class classic attributes. (If the class following the object, then the class is a new class), python3 the classes are new classes.

  property usage 2-- class attribute way

  When you create a property attribute using the class attribute way, Classic and new classes without distinction

class Test:
    def __init__(self):
        self.__num = 100

    def setNum(self, num):
        print("--set--")
        self.__num = num

    def getNum(self):
        print("--get--")
        return self.__num

    # 注意：要先写get方法，再写set方法
    aa = property(getNum, setNum)


t = Test()
print(t.aa)
t.aa = 1