New submission from David Beazley:
Suppose you subclass a dictionary:
class mdict(dict):
def __getitem__(self, index):
print('Getting:', index)
return super().__getitem__(index)
Now, suppose you define a function and perform these steps that reassign the
function's attribute dictionary:
>>> def foo():
... pass
...
>>> foo.__dict__ = mdict()
>>> foo.x = 23
>>> foo.x # Observe: No output from overridden __getitem__
23
>>> type(foo.__dict__)
<class '__main__.mdict'>
>>> foo.__dict__
{'x': 23}
>>>
Carefully observe that access to foo.x does not invoke the overridden
__getitem__() method in mdict. Instead, it just directly accesses the default
__getitem__() on dict.
Admittedly, this is a really obscure corner case. However, if the __dict__
attribute of a function can be legally reassigned, it might be nice for
inheritance to work ;-).
----------
components: Interpreter Core
messages: 179364
nosy: dabeaz
priority: normal
severity: normal
status: open
title: Function attribute access doesn't invoke methods in dict subclasses
type: behavior
versions: Python 3.3
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Python tracker <[email protected]>
<http://bugs.python.org/issue16894>
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