dict_utils.py

def dfs_visit_key(tree, key_re, visitor_fn):
    return dfs_walk(tree, \
                    lambda k, fk, val: \
                        visitor_fn(fk, val) \
                        if re.match(key_re, '.'.join(fk)) \
                        else val)

def dfs_walk(tree, visitor_fn, fullkey=None):
    fullkey = list(fullkey or [])
    if isinstance(tree, dict):  # subtree
        return dict([(k, dfs_walk(v, visitor_fn, fullkey + [k])) \
                     for k, v in tree.iteritems()])
    else:  # leaf
        k = fullkey[-1] if len(fullkey) else None
        return visitor_fn(k, fullkey, tree)