我正在与
__getattr__class A(object):
@property
def a(self):
raise AttributeError('lala')
def __getattr__(self, name):
print('attr: ', name)
return 1
print(A().a)
结果：
('attr: ', 'a')
1
__getattr__getattr()A.__dict__我刚刚将代码更改为
class A(object):
@property
def a(self):
print "trying property..."
raise AttributeError('lala')
def __getattr__(self, name):
print('attr: ', name)
return 1
print(A().a)
并且，正如我们所看到的，确实首先尝试了该属性。但由于它声称不在那里（通过提高
AttributeError__getattr__()它没有明确记录，但可以算在“当属性查找在通常的地方没有找到属性时调用”。
在同一个类中使用
__getattr__如果属性的 getter 抛出
AttributeErrorAttributeError__getattr____getattr____getattr__编辑：此问题的示例代码可以在这个答案中找到。
除非你的属性获取器很简单，否则你永远不能 100% 确定它不会抛出
AttributeError您可以这样做：
__getattr__try ... exceptAttributeError@propertyAttributeErrorRuntimeError另请参阅 http://blog.devork.be/2011/06/using-getattr-and-property_17.html
编辑：如果有人正在考虑解决方案 4（我不推荐），可以这样做：
def property_(f):
def getter(*args, **kwargs):
try:
return f(*args, **kwargs)
except AttributeError as e:
raise RuntimeError, "Wrapped AttributeError: " + str(e), sys.exc_info()[2]
return property(getter)
然后在覆盖
@property_@property__getattr____getattribute__如果该类还定义了
，则不会调用后者，除非__getattr__()显式调用它或引发__getattribute__()。AttributeError
我读到这篇文章（由 inclusio unius est exclusio alterius）说属性访问 will 调用
__getattr__object.__getattribute__AttributeError__get____get__AttributeError打个比方，运算符特殊方法可以引发
NotImplementedError__radd____add____getattr____getattr__但是
__getattr____getattr__经常遇到这个问题，因为我经常实现
__getattr__@propertydef replace_attribute_error_with_runtime_error(f):
@functools.wraps(f)
def wrapped(*args, **kwargs):
try:
return f(*args, **kwargs)
except AttributeError as e:
# logging.exception(e)
raise RuntimeError(
'{} failed with an AttributeError: {}'.format(f.__name__, e)
)
return wrapped
并像这样使用它：
class C(object):
def __getattr__(self, name):
...
@property
@replace_attribute_error_with_runtime_error
def complicated_property(self):
...
...
底层异常的错误消息将包含其实例引发底层
AttributeError无论如何，当你将
@property__getattr__class Paradise:
pass
class Earth:
@property
def life(self):
print('Checking for paradise (just for fun)')
return Paradise.breasts
def __getattr__(self, item):
print("sorry! {} does not exist in Earth".format(item))
earth = Earth()
try:
print('Life in earth: ' + str(earth.life))
except AttributeError as e:
print('Exception found!: ' + str(e))
给出以下输出：
Checking for paradise (just for fun)
sorry! life does not exist in Earth
Life in earth: None
当您真正的问题是打电话时
Paradise.breasts__getattr__
上升时，总是会调用
AtributeError可悲的是，这个问题没有解决方案，因为
hasattr(earth, 'life')True__getattr__Paradise.breasts我的部分解决方案涉及在
@propertyAttributeError我知道自从提出这个问题以来已经有一段时间了，但这是我的解决方法：
class PropertyAttributeError(Exception):
pass
def getattr_safe_property(func):
"""The A class uses 'property', and overloads
:obj:`__getattr__`. This is not a good idea, because if an AttributeError is
raised during the evaluation of a property, then the error message will
look like the property itself is not found.
To avoid those misleading errors, all properties of A must be written as such:
.. code-block:: python
@property
@getattr_safe_property
def some_property(self):
...
Since the new :obj:`~PropertyAttributeError` is raised from the original
:obj:`AttributeError`, the error stack will contain the actual problematic
line, but it will not be silently caught by :obj:`__getattr__`.
"""
def wrapper(self):
try:
return func(self)
except AttributeError as error:
raise PropertyAttributeError(
"An AttributeError was raised while evaluating the property "
f"'{func.__name__}' of a {self.__class__.__name__} instance:"
f" {error}"
) from error
return wrapper
class A:
def __init__(self):
self._a = 0
@property
@getattr_safe_property
def some_property(self):
return {}
def __getattr__(self, item):
# Do some stuff
raise AttributeError(f"No attribute {item}")
@property
@getattr_safe_property
def a(self):
print(self.some_property.wrong_attribute)
return self._a
@a.setter
def a(self, value):
self._a = value
b = A()
b.a = 3
print(b.a)
然后您将得到正确的错误堆栈：
Traceback (most recent call last):
File "path/to/file.py", line 8, in wrapper
return func(self)
^^^^^^^^^^
File "path/to/file.py", line 34, in a
print(self.some_property.wrong_attribute)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'dict' object has no attribute 'wrong_attribute'
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "path/to/file.py", line 44, in <module>
print(b.a)
^^^
File "/path/to/file.py", line 10, in wrapper
raise PropertyAttributeError(
PropertyAttributeError: An AttributeError was raised while evaluating the property 'a' of a A instance: 'dict' object has no attribute 'wrong_attribute'