A brief analysis of @property in Python decorators
1. Advantages of using @property
Convert class methods into class attributes, which can be used to directly obtain attribute values or assign values to attributes.
Case Analysis
Example:
class Exam(object):
def __init__(self, score):
self._score = score
def get_score(self):
return self._score
def set_score(self, val):
if val < 0:
self._score = 0
elif val > 100:
self._score = 100
else:
self._score = val
e = Exam(60)
print(e.get_score())
e.set_score(70)
print(e.get_score())
##Code analysis:
# defines an Exam class. In order to avoid direct operations on the _score attribute, the get_score and set_score methods are provided, so It plays the role of encapsulation, hiding some attributes that do not want to be exposed to the outside world, and only provides methods for users to operate. In the methods, the rationality of parameters can be checked, etc.
Python provides property decorators. The decorated methods can be used "as" properties.
Example:
class Exam(object):
def __init__(self, score):
self._score = score
@property
def score(self):
return self._score
@score.setter
def score(self, val):
if val < 0:
self._score = 0
elif val > 100:
self._score = 100
else:
self._score = val
e = Exam(60)
print(e.score)
e.score = 90
print(e.score)
e.score = 200
print(e.score)
##Note:
Add @property to the method score, so score can be used as a property. At this time, a new score.setter will be created, which can set the decorated method Become an attribute to assign a value to.In addition, you do not have to use the score.setter decorator, then score becomes a read-only property:
python处理上述问题的方法是使用property。可以这样来实现它。 例 : 并且，一旦运行，在shell中发出以下代码。 创建对象时，将调用init ()方法。此方法的线为self.temperature = temperature。 此分配自动称为set_temperature()。 任何访问如c.temperature都会自动调用get_temperature()。 例： 注： 温度值存储在私有变量_temperature中。temperature属性是一个属性对象，它提供了与此私有变量的接口。 在Python中，property()是一个内置函数，用于创建并返回属性对象。 语法 参数解析 fget为获取属性值的函数，fset为设置属性值的函数，fdel为删除属性的函数，doc为字符串(如注释)。从实现中可以看出，这些函数参数是可选的。 可以简单地按照以下方式创建属性对象。 语法: 用于稍后指定fget、fset和fdel。 注： 这两段代码是等效的。 不定义名称get_temperature，set_temperature。 因为它们是不必要的，并且会影响类命名空间。为此，在定义getter和setter函数时重用了名称temperature。 例： 注： 实现是制作属性的简单方法和推荐方法。在Python中寻找属性时，很可能会遇到这些类型的构造。 本文基于Python基础，介绍了@property 如何把方法变成了属性。通过案例的分析，代码的展示。介绍了@property的力量，以及提供了相应错误的解决方案处理方法。属性的作用。 The above is the detailed content of A brief analysis of @property in Python decorators. For more information, please follow other related articles on the PHP Chinese website!class Exam(object):
def __init__(self, score):
self._score = score
@property
def score(self):
return self._score
e = Exam(60)
print(e.score)
e.score = 200 # score 是只读属性，不能设置值
print(e.score)
二、@property的力量
class Celsius:
def __init__(self, temperature = 0):
self.temperature = temperature
def to_fahrenheit(self):
return (self.temperature * 1.8) + 32
def get_temperature(self):
print("获得的值")
return self._temperature
def set_temperature(self, value):
if value < -273:
raise ValueError("零下273度是不可能的")
print("设定值")
self._temperature = value
temperature = property(get_temperature,set_temperature)c = Celsius()
print(c.temperature)
2. 属性的作用。
c.temperature = 37
print(c.temperature)
print(c.to_fahrenheit())
三、深入了解property
property(fget=None, fset=None, fdel=None, doc=None)
property(fget=None, fset=None, fdel=None, doc=None)
print(property())
1. 属性对象有三个方法，getter()、setter()和deleter()。
temperature = property(get_temperature,set_temperature)
# 创建空属性
temperature = property()
# 设置 fget
temperature = temperature.getter(get_temperature)
# 设置 fset
temperature = temperature.setter(set_temperature)
2. 案例
class Celsius:
def __init__(self, temperature = 0):
self._temperature = temperature
def to_fahrenheit(self):
return (self.temperature * 1.8) + 32
@property
def temperature(self):
print("获得值")
return self._temperature
@temperature.setter
def temperature(self, value):
if value < -273:
raise ValueError("零下273度是不可能的")
print("零下273度是不可能的")
self._temperature = value
c=Celsius()
c.temperature = 37
print(c.temperature)
四、总结
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