Find a dict key from its value

gistfile1.py

def reverse_dict_lookup(d, val):
    """
    Performs a reverse lookup on a dictionary object, raising ValueError on
    failure.

    >>> reverse_dict_lookup({'a': 1, 'b': 2, 'c': 3}, 2)
    'b'
    >>> reverse_dict_lookup({}, 'a')
    Traceback (most recent call last):
        ...
    ValueError
    """
    try:
        return (key for key, value in d.items() if value == val).next()
    except StopIteration:
        raise ValueError