关于#keyerro#的问题，如何解决？

Question

这是什么情况呀 有兄弟能帮忙解答一下吗

 target_list = {}
        for ks in key_sentences:
            # print ks
            words = T.postag(ks)
            for w in words:
                # print "====="
                # print w.word
                if w.flag == ("nr"):
                    if w.word not in target_list:
                        target_list[w.word] += 1
                    else:
                        target_list[w.word] = 1

Traceback (most recent call last):
  File "D:/IJspace/QA-Snake-master/QA/MainProgram.py", line 102, in <module>
    ans = search_summary.kwquery(input_message)
  File "D:\IJspace\QA-Snake-master\QA\QACrawler\search_summary.py", line 262, in kwquery
    target_list[w.word] += 1
KeyError: '释永信'

Answer 1

if w.word not in target_list:
                        target_list[w.word] += 1

+= 换成 =，你都不存在了，当然不能 += 运算