gistfile1.py

import collections

class DumbMap(collections.MutableMapping):
    def __init__(self):
        elements = []
    def __getitem__(self, key):
        for k, v in self.elements.iteritems():
            if k == key:
                return v
        else:
            raise KeyError(key)
    def __setitem__(self, key, value):
        if key in self:
            del self[key]
        self.elements.append((key, value))
    def __delitem__(self, key):
        if key not in self:
            raise KeyError(key)
        self.elements = [(k, v) for (k, v) in self.elements if k != key]
    def __iter__(self):
        return iter(k for k, v in self.elements)
    def __len__(self):
        return len(self.elements)

def weird_merge(a, b):
    rv = list(a)
    a_elements = DumbMap()
    for x in a:
        a_elements[x] = a_elements.get(x, 0) + 1
    for x in b:
        if a_elements.get(x, 0) > 0:
            a_elements[x] -= 1
            continue
        rv.append(x)
    return rv