user-supplied locals dict for function execution?

Ziga Seilnacht ziga.seilnacht at
Tue Mar 21 17:13:05 CET 2006

Lonnie Princehouse wrote:
> Occaisionally, the first two lines of The Zen of Python conflict with
> one another.
> An API I'm working on involves a custom namespace implementation using
> dictionaries, and I want a pretty syntax for initializing the custom
> namespaces.  The fact that these namespaces are implemented as
> dictionaries is an implementation detail, and I don't want the users to
> access them directly.  I find the "implicit update" syntax to be much
> cleaner:

This can be easier achieved with a custom metaclass:

>>> class MetaNamespace(type):
...     def __new__(metaclass, name, bases, dict):
...         try:
...             Namespace
...         except NameError:
...             return type.__new__(metaclass, name, bases, dict)
...         dict.pop('__module__', None)
...         return dict
>>> class Namespace(object):
...     __metaclass__ = MetaNamespace

Now whenever you want to create your dictionary you simply
declare a class that inherits from Namespace:

>>> class MyNamespace(Namespace):
...     x = 5
...     y = 'spam'
...     z = 'eggs'
>>> print sorted(MyNamespace.items())
[('x', 5), ('y', 'spam'), ('z', 'eggs')]


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