def flatten_json(j):
    for k, v in j.items():
        if isinstance(v, dict):
            yield from flatten_json(v)
        else:
            yield (k,v)


j = {'foo': 'bar', 'foo1': 'bar1', 'nest1': {'foo2': 'bar2'}}
flat_json = {x[0]: x[1] for x in flatten_json(j)}
print(flat_json)