Python practical Note (23) object-oriented advanced programming-using @property

This is obviously illogical. To limit the scope of the score, you can set the score by one method, and set_score() then get the score by one, get_score() so that in the set_score() method, you can check the parameters:

 class studentdef get_scorereturn self._score def set_scoreif not Isinstance (value, int): raise valueerror ( ' score must is an integer! ') if value < 0 or value >  100: span class= "keyword" >raise valueerror ( ' score must between 0 ~ 100! ') Self._score = value  span>                 

Remember the adorner (decorator) can add functionality to a function dynamically? For class methods, adorners work as well. Python's built-in @property adorner is responsible for turning a method into a property call:

class student (object): @ Property def scorereturn self._score  @score. Setter def score (self, value): if not isinstance (value, int): raise valueerror (if value < 0 or value >  : raise valueerror ( ' score must between 0 ~ 100! ') Self._score = value
                                            

@propertyImplementation is more complex, we first examine how to use. To turn a getter method into a property, just add it, and @property at this point, it @property creates another adorner @score.setter , which is responsible for turning a setter method into a property assignment, so we have a controllable property operation:

>>> s = Student()>>> s.score = 60 # OK，实际转化为s.set_score(60)>>> s.score # OK，实际转化为s.get_score()60>>> s.score = 9999Traceback (most recent call last): ...ValueError: score must between 0 ~ 100!

Notice that this magical @property , when we operate on instance properties, we know that this property is probably not directly exposed, but is implemented through getter and setter methods.

Python practical Note (23) object-oriented advanced programming-using @property