Extended Dictionary class for searching keys

ordered_dict.py

class ExtendedOrderedDict(OrderedDict):
    """Extended version of the OrderedDict with more methods.

    This class adds the 'next_key' and 'first_key' to easily traverse through
    an ordered dictionary. It's meant to be inherited by any OrderedDict
    structure.
    """

    def get_next_key(self, key):
        key_list = list(self.keys())
        key_position = key_list.index(key)
        if key_position < len(key_list) - 1:
            return key_list[key_position + 1]
        else:
            raise IndexError("{} is already the last key.".format(key_position))

    def get_previous_key(self, key):
        key_list = list(self.keys())
        key_position = key_list.index(key)
        if key_position > 0:
            return key_list[key_position - 1]
        else:
            raise IndexError("{} is already the first key.".format(key_position))