How to read class attributes in the same order as declared?

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In the current version of Python, the class ordering is preserved. See PEP520 for details.

In older versions of the language (3.5 and below, but not 2.x), you can provide a metaclass which uses an OrderedDict for the class namespace. 

import collections 

class OrderedClassMembers(type):
    @classmethod
    def __prepare__(self, name, bases):
        return collections.OrderedDict()

    def __new__(self, name, bases, classdict):
        classdict['__ordered__'] = [key for key in classdict.keys()
                if key not in ('__module__', '__qualname__')]
        return type.__new__(self, name, bases, classdict)

class Something(metaclass=OrderedClassMembers):
    A_CONSTANT = 1

    def first(self):
        ...

    def second(self):
        ...

print(Something.__ordered__)
# ['A_CONSTANT', 'first', 'second']

This approach doesn’t help you with existing classes, however, where you’ll need to use introspection.

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