TypeError：*之后的参数encrypt（）必须是一个序列，而不是NoneType

Question

有人可以帮我解释为什么它给这个TypeError？

这里是check_args函数定义：（此代码是从欧文斯·斯蒂芬斯AES基于代码）

def check_args(): 
    try: 
     if (len(sys.argv) != 4): 
      raise Exception() 
     elif (not os.path.isfile(sys.argv[1])): 
      raise Exception("Input file must exist") 
     elif (not sys.argv[3] in ['CBC', 'ECB']): 
      raise Exception("Block cipher mode should be ECB or CBC") 
      return (sys.argv[1], sys.argv[2], sys.argv[3]) 
    except Exception as ex: 
     print ("Usage:", sys.argv[0], "full_path_to_input_image full_path_to_output_image ECB|CBC") 
     if len(ex.args) > 0: 
      print ("--" + str(ex)) 
      sys.exit(1) 



if __name__ == "__main__": 
    args = check_args() 
    encrypt(*args) 

    Traceback (most recent call last): 
     File " ", line 57, in <module> 
     encrypt(*args) 
    TypeError: encrypt() argument after * must be a sequence, not NoneType 

Answer 1

的return语句缩进一个层次太多。放下它。