generate_combinations.py

import itertools

DIMENSIONS = {
    'city': [
        'sf', 'nyc', 'la', 'chicago',
    ],

    'color': [
        'red', 'orange', 'yellow', 'green', 'blue', 'indigo', 'violet',
    ],

    'car_make': [
        'porsche', 'audi', 'bmw', 'tesla',
    ],
}


def to_list(x):
    return x if type(x) == list else [x]


def project_combinations(spec):
    resolved = {}
    for k, v in spec.iteritems():
        resolved_vals = []
        for o in to_list(v):
            if type(o) == dict:
                resolved_vals.extend(to_list(project_combinations(o)))
            else:
                resolved_vals.append(o)
        resolved[k] = resolved_vals

    return expand_combinations_dict(resolved)


def expand_combinations_dict(o):
    '''
    Given a dict whose keys map to one or more values, return a list of dicts
    representing all combinations of those values:

    Example:

       input = {
         'first_name': ['Alice', 'Bob', 'Clyde'],
         'last_name': 'Smith',
       }

       expand_combinations_dict(input)
         => [
           {'first_name': 'Alice', 'last_name': 'Smith'},
           {'first_name': 'Bob', 'last_name': 'Smith'},
           {'first_name': 'Clyde', 'last_name': 'Smith'},
         ]

    '''
    combo_tuples = []
    for k, v in o.iteritems():
        key_tuples = list(itertools.product([k], to_list(v)))
        combo_tuples.append(key_tuples)

    combinations = itertools.product(*combo_tuples)
    return [dict(c) for c in combinations]'
    
    
if __name__ == '__main__':
    print project_combinations(DIMENSIONS)

Nice.