How to know execute_async correctly?

[lampahome]

I tried to execute async by batch in python-driver. But I don't know how to
check query executing correctly.

Code is like below:
B = BatchStatement()
for x in xxx:
    B.add(query, (args))
res = session.execute_async(B)
B.clear() # for reusing
r = res.result()
## Then how to know my query works correctly? print(r)?


I found no doc about my question in the page of ResultSet.
Can anyone explain?

thx