Eric V. Smith <[email protected]> added the comment:
But this is no different from every other mutable class variable in Python:
class Base:
data = {}
class Alpha(Base):
pass
class Beta(Base):
data = {}
Alpha.data['injected'] = bool
assert Alpha.data is Base.data
Beta.data['injected'] = bool
I'm not sure what could change here. The choices seem to be break a lot of
existing code and have new behavior for all class variables, or do something
special for __annotations__.
In general, to get what you want, you'd need to do something like this (going
back to your original example):
def add_annotation(cls, v, t):
if not "__annotations__" in cls.__dict__:
# Doesn't exist, add it.
cls.__annotations__ = {}
cls.__annotations__[v] = t
add_annotation(Base, 'a', int)
add_annotation(Alpha,'a', float)
add_annotation(Beta, 'a', str)
Which produces:
{'base': <class 'int'>, 'a': <class 'int'>}
{'a': <class 'float'>}
{'foobar': <class 'int'>, 'a': <class 'str'>}
Again, this is just how class variables work in Python.
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<https://bugs.python.org/issue40583>
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