How are Counter / defaultdict ordered in Python 3.7?

Counter and defaultdict are both ordered now, and you can rely on it. Counter just doesn't look ordered because its repr was designed before dict ordering was guaranteed, and Counter.__repr__ sorts entries by descending order of value.

def __repr__(self):
    if not self:
        return '%s()' % self.__class__.__name__
    try:
        items = ', '.join(map('%r: %r'.__mod__, self.most_common()))
        return '%s({%s})' % (self.__class__.__name__, items)
    except TypeError:
        # handle case where values are not orderable
        return '{0}({1!r})'.format(self.__class__.__name__, dict(self))