eventtest.py

class Result(threading.Event):
    exception = None


def execute():
    cql = 'select * from events limit 10'
    response = Result()
    
    def _on_error(error):
        response.exception = error
        response.set()
        
    def _on_complete(results):
        try:
            do_something(results)
        except BaseException as exc:
            response.exception = exc
        finally:
            response.set()
        
    future = session.execute_async(cql)
    future.add_callbacks(_on_results, _on_error)
    return response
    
def main():
    result = execute()
    result.wait()
    if result.exception:
        raise result.exception