Thought I knew how to provide a dynamic __name__ on instances of a
class. My first try was to use a non-data descriptor:
# module base.py
class _NameProxy(object):
def __init__(self, oldname):
self.oldname = oldname
def __get__(self, obj, cls):
if obj is None:
return self.oldname
if "__name__" not in obj.__dict__:
return str(obj.__context__)
return obj.__name__
class _BaseMeta(type):
def __init__(cls, name, bases, namespace):
cls.__name__ = _NameProxy(name)
class Base(object):
__metaclass__ = _BaseMeta
$ python _base.py
Traceback (most recent call last):
...
File "/usr/local/lib/python2.4/site-packages/base.py", line xx, in __init__
cls.__name__ = _NameProxy(name)
TypeError: Error when calling the metaclass bases
can only assign string to Base.__name__, not '_NameProxy'
Needless to say I was surprised. After looking in typeobject.c, I
believe that __name__ must be a string where classes are concerned[1].
So if I want all my instances to have a __name__ attribute, and for
it to be dynamically provided if it isn't set on the instance, what
are my options? Or maybe I did something wrong and it should work as
I expected?
-eric
[1] http://hg.python.org/cpython/file/default/Objects/typeobject.c#l244
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