from collections import OrderedDict def recursive_test(leaf, fn): if isinstance(leaf, list): if fn(leaf[0]): return leaf else: return None else: _leaf = {} try: for key, val in leaf.items(): cur_leaf = recursive_test(val, fn) if cur_leaf: _leaf[key] = cur_leaf return _leaf or None except AttributeError: if fn(leaf): return leaf a = { 'a': None, 'b': 4, 'c': { 'd': None, 'e': "test", 'f': { 'g': 1, 'h': None } } } print(recursive_test(a, lambda x: x is not None))