How does one get an Enum's members into the global namespace?

Question

Python now has an Enum type (new in 3.4 with PEP 435, and alse backported), and while namespaces are a good thing, sometimes Enums are used more like constants, and the enum members should live in the global (er, module) namespace.

So instead of:

Constant(Enum):
    PI = 3.14

...

area = Constant.PI * r * r

I can just say:

area = PI * r * r

Is there an easy way to get from Constant.PI to just PI?

Answer 1

The officially supported method is something like this:

globals().update(Constant.__members__)

This works because __members__ is the dict-like object that holds the names and members of the Enum class.

I personally find that ugly enough that I usually add the following method to my Enum classes:

@classmethod
def export_to(cls, namespace):
    namespace.update(cls.__members__)

and then in my top level code I can say:

Constant.export_to(globals())

Note: exporting an Enum to the global namespace only works well when the module only has one such exported Enum. If you have several it is better to have a shorter alias for the Enum itself, and use that instead of polluting the global namespace:

class Constant(Enum):
    PI = ....
C = Constant

area = C.PI * r * r