[issue44003] functools.lru_cache omits __defaults__ attribute from wrapped function
Raymond Hettinger
report at bugs.python.org
Sat May 1 21:29:01 EDT 2021
Raymond Hettinger <raymond.hettinger at gmail.com> added the comment:
I don't really like it. Carrying forward these attributes isn't the norm for wrapping functions.
The __defaults__ argument is normally only used where it has an effect rather than in a wrapper where it doesn't. Given that it is mutable, it invites a change that won't work. For example:
>>> def pow(base, exp=2):
return base ** exp
>>> pow.__defaults__
(2,)
>>> pow.__defaults__ = (3,)
>>> pow(2)
8
Also, an introspection function can only meaningfully use defaults when accompanied by the names of the fields:
>>> pow.__code__.co_varnames
('base', 'exp')
However, these aren't visible by directly introspecting the wrapper.
FWIW, we've never had a user reported issue regarding the absence of __defaults__. If ain't broke, let's don't "fix" it.
Nick and Serhiy, any thoughts?
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