def update(dest, upd, recursive_update=True, merge_lists=False):
    if (not isinstance(dest, collections.Mapping)) \
            or (not isinstance(upd, collections.Mapping)):
        raise TypeError('Cannot update using non-dict types in dictupdate.update()')
    updkeys = list(upd.keys())
    if not set(list(dest.keys())) & set(updkeys):
        recursive_update = False
    if recursive_update:
        for key in updkeys:
            val = upd[key]
            try:
                dest_subkey = dest.get(key, None)
            except AttributeError:
                dest_subkey = None
            if isinstance(dest_subkey, collections.Mapping) \
                    and isinstance(val, collections.Mapping):
                ret = update(dest_subkey, val, merge_lists=merge_lists)
                dest[key] = ret
            elif isinstance(dest_subkey, list) \
                     and isinstance(val, list):
                if merge_lists:
                    dest[key] = dest.get(key, []) + val
                else:
                    dest[key] = upd[key]
            else:
                dest[key] = upd[key]
        return dest
    else:
        try:
            dest.update(upd)
        except AttributeError:
            # this mapping is not a dict
            for k in upd:
                dest[k] = upd[k]
        return dest
Recursive version of the default dict.update
dataset/ETHPy150Open saltstack/salt/salt/utils/dictupdate.py/update