inspect.getmembers in order?

Question

inspect.getmembers(object[, predicate])

Return all the members of an object in a list of (name, value) pairs sorted by nam

Answer 1

I don't think Python 2.6 has a __prepare__ method, so I can't swap out the default dict for an ordered one. I can, however, replace it using a metaclass and the __new__ method. Instead of inspecting line numbers, I think its easier and more efficient to just use a creation counter.

class MetaForm(type):
    def __new__(cls, name, bases, attrs):
        attrs['fields'] = OrderedDict(
            sorted(
                [(name, attrs.pop(name)) for name, field in attrs.items() if isinstance(field, Field)],
                key=lambda t: t[1].counter
            )
        )
        return type.__new__(cls, name, bases, attrs)

class Form(object):
    __metaclass__ = MetaForm

class Field(object):
    counter = 0
    def __init__(self):
        self.counter = Field.counter
        Field.counter += 1