python使用multiprocessing模块实现带回调函数的异步调用方法

from multiprocessing import Pool
def f(x):
  return x*x
if __name__ == '__main__':
  pool = Pool(processes=1)
  # Start a worker processes.
  result = pool.apply_async(f, [10], callback) 
  # Evaluate "f(10)" asynchronously calling callback when finished.