Is it possible to make a module iterable in Python?

Question

I am making a module that I want to treat as a static container of objects. These objects are of a class type that I have defined. I want to be able to import this module and then loop over the objects within. Here is some code explaining what I mean:

example.py

class MyExampleClass(object):
    def __init__(self, var1, var2, var3):
        self.var1 = var1
        self.var2 = var2
        self.var3 = var3
        self.var4 = var4

instanceA = MyExampleClass(1, 2, 3, 4)
instanceB = MyExampleClass(4, 3, 6, 7)
instanceC = MyExampleClass(5, 3, 4, 5)

# something like this
def __iter__():
    return (instanceA, instanceB, instanceC)

Then I would like to be able to import this and use it like an enum:

import example

for e in example:
   # do stuff with e

Is this possible to do in Python? Or will I have to import a list from within the example package?

example.py

objects = (instanceA, instanceB, instanceC)

and then

import example

for e in example.objects:
    # do stuff with e

Answer 1

You can achieve that by defining a root class in your module and replacing the module with an instance of that class. Here is an example:

class ModuleClass(object):
    __init__(self):
        self.instanceA = MyExampleClass(1, 2, 3, 4)
        ...

    __iter__(self):
        # Your iterator logic here

# and then in the same module code
sys.modules[__name__] = ModuleClass()

So then you can do what you want, because when you import that module, it will actually be an instance of your custom iterable ModuleClass:

import example

for e in example:
   # do stuff with e

Answer 2

Although I do not recommend it, you can build your own module by inheriting from types.ModuleType. You can then replace the original module with your custom class with sys.modules[__name__] = NewModule()

import types
import sys

class MyExampleClass(object):
    def __init__(self, var1, var2, var3, var4):
        self.var1 = var1
        self.var2 = var2
        self.var3 = var3
        self.var4 = var4

class MyModule(types.ModuleType):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.instanceA = MyExampleClass(1, 2, 3, 4)
        self.instanceB = MyExampleClass(4, 3, 6, 7)
        self.instanceC = MyExampleClass(5, 3, 4, 5)

    def __iter__(self):
        return iter([self.instanceA, self.instanceB, self.instanceC])

sys.modules[__name__] = MyModule("example") # Name of the module