Python中的NoneType錯誤

Question

我運行這段代碼，但我得到了typeError：'NoneType'對象不可迭代 什麼是問題？

import bibtex 
import unittest 

class TestAuthorExtract(unittest.TestCase): 
    def setUp(self): 
     self.simple_author_1 = "Smith" 

    def test_author_1(self): 
     # Test only surname 
     (Surname , FirstNames) = bibtex.extract_author(self.simple_author_1) 
     self.assertEqual((Surname , FirstNames) , ("Smith", "")) 

if __name__=='__main__': 
    unittest.main() 

以下是錯誤消息：

====================================================================== 
ERROR: test_author_1 (main.TestAuthorExtract) 
---------------------------------------------------------------------- 
Traceback (most recent call last): 
    File "div.py", line 10, in test_author_1 
    (Surname , FirstNames) = bibtex.extract_author(self.simple_author_1) 
    TypeError: 'NoneType' object is not iterable 
---------------------------------------------------------------------- 
Ran 1 test in 0.001s FAILED (errors=1) 

Answer 1

這意味着，bibtex.extract_author()返回None。之後，解釋器試圖將該值分配給元組(Surname, Firstname)，這隻能用長度爲2的迭代器（稱爲unpacking）完成。