Dict と List のネストしたものから、プリミティブなものを取り出す。（例えば JSON とか。）

unstructure.py

# coding: utf8
import types


def unstructure(structured, usedictkey=True, usedictvalue=True):
    if isinstance(structured, dict):
        for keys, values in structured.iteritems():
            if usedictkey:
                for key in unstructure(keys):
                    yield key
            if usedictvalue:
                for value in unstructure(values):
                    yield value
    elif isinstance(structured, (list, tuple, xrange, types.GeneratorType)):
        for items in structured:
            for item in unstructure(items):
                yield item
    else:
        yield structured


if __name__ == '__main__':
    test = {
        'x': ['y', 'z'],
        'z': [
            {
                'w': {
                    's': ['a']
                }
            }
        ]
    }
    from collections import Counter
    c = Counter()
    for token in unstructure(test):
        c[token] += 1
    assert dict(c) == {'x': 1, 'y': 1, 'z': 2, 'w': 1, 's': 1, 'a': 1}