[Python-ideas] objects aware of being bound to a name

Carl M. Johnson cmjohnson.mailinglist at gmail.com
Sun Jun 5 10:00:55 CEST 2011

This is in principle doable with metaclasses (like everything else :-D)...

Here's what I whipped up in the console:

>>> class MagicDict(dict):
...     def __setitem__(self, key, value):
...         print("Binding key: {} to value: {}".format(key, value))
...         if hasattr(value, "__bind__"):
...             value.__bind__(key)
...         super().__setitem__(key, value)
>>> class Bindable:
...     def __bind__(self, key):
...         print("{} was bound to {}".format(self, key))
>>> class MetaBinding(type):
...     @classmethod
...     def __prepare__(metacls, name, bases):
...        return MagicDict()
>>> class BindingReports(metaclass=MetaBinding):
...     a = 1
...     b = Bindable()
...     c = "blah"
Binding key: __module__ to value: __main__
Binding key: a to value: 1
Binding key: b to value: <__main__.Bindable object at 0x100603b50>
<__main__.Bindable object at 0x100603b50> was bound to b
Binding key: c to value: blah

Not sure how useful this is. I don't like using the term "class" for things
where you're not really trying to bundle together methods or create a type,
just change the way values get bound.

-- Carl Johnson
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