Function _copy_future_state

Lib/asyncio/futures.py:355–370

Internal helper to copy state from another Future. The other Future must be a concurrent.futures.Future.

(source, dest)

def _copy_future_state(source, dest):
    """Internal helper to copy state from another Future.

    The other Future must be a concurrent.futures.Future.
    """
    if dest.cancelled():
        return
    assert not dest.done()
    done, cancelled, result, exception = source._get_snapshot()
    assert done
    if cancelled:
        dest.cancel()
    elif exception is not None:
        dest.set_exception(_convert_future_exc(exception))
    else:
        dest.set_result(result)

def _chain_future(source, destination):
    """Chain two futures so that when one completes, so does the other.