Namespaces inside class in Python3

user_6185103 0
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I am new to Python and I wonder if there is any way to aggregate methods into 'subspaces'. I mean something similar to this syntax:

smth = Something()
smth.subspace.do_smth()
smth.another_subspace.do_smth_else()

I am writing an API wrapper and I'm going to have a lot of very similar methods (only different URI) so I though it would be good to place them in a few subspaces that refer to the API requests categories. In other words, I want to create namespaces inside a class. I don't know if this is even possible in Python and have know idea what to look for in Google.

I will appreciate any help.

python-3.x namespaces class python
2 Answers

I had this need a couple years ago and came up with this:

class Registry:
    """Namespace within a class."""

    def __get__(self, obj, cls=None):
        if obj is None:
            return self
        else:
            return InstanceRegistry(self, obj)

    def __call__(self, name=None):

        def decorator(f):
            use_name = name or f.__name__
            if hasattr(self, use_name):
                raise ValueError("%s is already registered" % use_name)
            setattr(self, name or f.__name__, f)
            return f

        return decorator


class InstanceRegistry:
    """
    Helper for accessing a namespace from an instance of the class.

    Used internally by :class:`Registry`. Returns a partial that will pass
    the instance as the first parameter.
    """

    def __init__(self, registry, obj):
        self.__registry = registry
        self.__obj = obj

    def __getattr__(self, attr):
        return partial(getattr(self.__registry, attr), self.__obj)


# Usage:

class Something:
    subspace = Registry()
    another_subspace = Registry()

@MyClass.subspace()
def do_smth(self):
    # `self` will be an instance of Something
    pass

@MyClass.another_subspace('do_smth_else')
def this_can_be_called_anything_and_take_any_parameter_name(obj, other):
    # Call it `obj` or whatever else if `self` outside a class is unsettling
    pass

At runtime:

>>> smth = Something()
>>> smth.subspace.do_smth()
>>> smth.another_subspace.do_smth_else('other')

This is compatible with Py2 and Py3. Some performance optimizations are possible in Py3 because __set_name__ tells us what the namespace is called and allows caching the instance registry.

user_789030
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