getattr(obj, self.UNIQUE_KEY)属性是什么
时间: 2024-05-31 20:08:54 浏览: 16
无法确定,因为不知道self.UNIQUE_KEY是什么。
一般来说,getattr(obj, attr)是Python内置函数之一,用于获取对象obj的属性attr的值。如果对象不存在该属性,则会引发AttributeError异常。
在这种情况下,self.UNIQUE_KEY是一个变量或字符串,它的值不确定,因此无法确定getattr(obj, self.UNIQUE_KEY)的确切含义。
相关问题
self.__getattr__
self.__getattr__ is a special method in Python that is used to define what happens when an attribute that does not exist is accessed on an object. It is called automatically by Python when an attribute lookup fails, and it can be used to dynamically generate attributes or to redirect attribute access to other objects.
For example, let's say we have a class called Person that has a dictionary attribute called info. We can use __getattr__ to allow accessing the keys of the info dictionary directly on the Person object:
```
class Person:
def __init__(self, name):
self.name = name
self.info = {'age': 30, 'city': 'New York'}
def __getattr__(self, name):
if name in self.info:
return self.info[name]
else:
raise AttributeError(f"'{self.__class__.__name__}' object has no attribute '{name}'")
```
Now we can create a Person object and access the age and city attributes directly:
```
p = Person('John')
print(p.age) # Output: 30
print(p.city) # Output: New York
```
If we try to access an attribute that doesn't exist in the info dictionary, we'll get an AttributeError:
```
print(p.gender) # Output: AttributeError: 'Person' object has no attribute 'gender'
```
def __getattr__(self, attr): if attr in self.meters: return self.meters[attr] if attr in self.__dict__: return self.__dict__[attr] raise AttributeError("'{}' object has no attribute '{}'".format( type(self).__name__, attr))
这段代码是`MetricLogger`类的一个特殊方法`__getattr__`,用于在访问对象的属性时进行处理。
当访问一个属性时,如果该属性存在于`self.meters`字典中,则返回字典中对应的值。这意味着可以通过直接访问`MetricLogger`对象的属性来获取相应指标的`SmoothedValue`对象。
如果属性不存在于`self.meters`字典中,但存在于`self.__dict__`字典中(即对象的其他属性),则返回`self.__dict__[attr]`。
如果既不在`self.meters`字典中,也不在`self.__dict__`字典中,则抛出一个`AttributeError`异常,指示该对象没有该属性。
总而言之,`__getattr__`方法允许通过直接访问对象的属性来获取指标的`SmoothedValue`对象,并提供了属性不存在时的异常处理。
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