using itertools's chain and groupby to merge a list of dictionaries

merge_dicts.py

def merge_dicts(dict_list):
    """Merge all values from dict list into a single dict

    >>> d1 = {'a': 1, 'b': 2}
    >>> d2 = {'a': 2, 'b': 3}
    >>> merge_dicts([d1, d2])
    {'a': [1, 2], 'b': [2, 3]}

    """
    kviter = chain.from_iterable(d.iteritems() for d in dict_list)
    grouped = groupby(sorted(kviter), itemgetter(0))
    return dict((k, [v for _, v in group]) for k, group in grouped)