Extra AttributeError inside property - possible bug ?
dunric29a at gmail.com
dunric29a at gmail.com
Tue Sep 1 00:56:46 EDT 2015
Hello,
bellow is a simple Python2 example of a class which defines __getattr__ method and a property, where AttributeError exception is raised:
from __future__ import print_function
class MyClass(object):
def __getattr__(self, name):
print('__getattr__ <<', name)
raise AttributeError(name)
return 'need know the question'
@property
def myproperty(self):
print(self.missing_attribute)
return 42
my_inst = MyClass()
print(my_inst.myproperty)
# produces following output
__getattr__ << missing_attribute
__getattr__ << myproperty
Traceback (most recent call last):
File "a.py", line 84, in <module>
main()
File "a.py", line 74, in main
print('==', my_inst.myproperty)
File "a.py", line 36, in __getattr__
raise AttributeError(name)
AttributeError: myproperty
By the documentation https://docs.python.org/2/reference/datamodel.html#object.__getattr__ , if class defines __getattr__ method, it gets called at AttributeError exception and should return a computed value for name, or raise (new) AttributeError exception.
Why is __getattr__ called 2nd time, with 'myproperty' argument ?!?
self.myproperty does exist and also at first call of __getattr__ new AttributeException with 'missing_attribute' is raised. I can't see any reason for this behavior.
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