Flatten nested dicts

flatten_dict.py

def flatten_dict(d):
    def expand(key, value):
        if isinstance(value, dict):
            return [(key + '.' + k, v) for k, v in flatten_dict(value).items()]
        else:
            return [(key, value)]

    items = [item for k, v in d.items() for item in expand(k, v)]

    return dict(items)