Python:正则表达式单词匹配

我写了这个小脚本，但我无法让 re.search 函数正常工作。我试图只匹配确切的词(笑话)，但 elif 语句一直返回打印，因为它在句子变量中找到了笑话(来自 clown )。有什么方法可以让它计算笑话这个词中的字母数量，所以只有当笑话是一个独立的词时它才正确？

#!/usr/bin/python 
import re 
 
sentence = 'The substantial treat shouts with the jokers' 
find_emergency = re.search( r'emergency', sentence, re.M|re.I) 
find_joke = re.search( r'joke', sentence, re.M|re.I) 
 
if find_emergency : 
   print 'Do you want to set this email as urgent?' 
elif find_joke :   
  print "Do you want to mark this email as non-urgent?" 
else : 
   print "Sorry, we couldn\'t find what you were looking for ;(" 

请您参考如下方法:

find_joke = re.search( r'\bjoke\b', sentence, re.M|re.I) 

为此使用 \b 或 word boundary。