back in Python 2.1 (and before), an object could define how copy.copy should
work simply by definining a __copy__ method. here's the relevant portion:
...
try:
copierfunction = _copy_dispatch[type(x)]
except KeyError:
try:
copier = x.__copy__
except AttributeError:
raise error, \
"un(shallow)copyable object of type %s" % type(x)
y = copier()
...
I recently discovered that this feature has disappeared in 2.3 and 2.4. in-
stead of looking for an instance method, the code now looks at the object's
type:
...
cls = type(x)
copier = _copy_dispatch.get(cls)
if copier:
return copier(x)
copier = getattr(cls, "__copy__", None)
if copier:
return copier(x)
...
(copy.deepcopy still seems to be able to use __deepcopy__ hooks, though)
is this a bug, or a feature of the revised copy/pickle design? (the code in
copy_reg/copy/pickle might be among the more convoluted pieces of python
coding that I ever seen... and what's that smiley doing in copy.py?)
and if it's a bug, does the fact that nobody reported this for 2.3 indicate that
I'm the only one using this feature? is there a better way to control copying
that I should use instead?
</F>
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