A nasty deep dictionary apply utility

deep_dict_apply.py

def deep_dict_apply(d, k_fn=None, v_fn=None):
    """
    >>> def k_fn(key):
    ...     return str(key) + "_k"
    >>> def v_fn(value):
    ...     return str(value) + "_v"
    >>> dictionary = {1: {2: {3: 'hello'}}, 4: 'world'}
    >>> deep_dict_apply(dictionary, k_fn, v_fn)
    {'4_k': 'world_v', '1_k': {'2_k': {'3_k': 'hello_v'}}}
    >>> deep_dict_apply(dictionary, k_fn)
    {'4_k': 'world', '1_k': {'2_k': {'3_k': 'hello'}}}
    >>> deep_dict_apply(dictionary, v_fn=v_fn)
    {1: {2: {3: 'hello_v'}}, 4: 'world_v'}
    """
    return dict([(k_fn and k_fn(k) or k, isinstance(v, dict) and deep_dict_apply(v, k_fn, v_fn) or v_fn and v_fn(v) or v) for k, v in d.items()])