Python:在字符串中查找单词

Question

我正在尝试用Python在字符串中找到一个单词.

str1 = 'This string'
if 'is' in str1:
    print str1

在上面的例子中,我希望它不打印str1.虽然在下面的例子中,我希望它打印str2.

str2 = 'This is a string'
if 'is' in str2:
    print str2

我将如何在Python中执行此操作？

Answer 1

将字符串拆分为单词并搜索它们:

if 'is' in str1.split(): # 'is' in ['This', 'string']
    print(str1) # never printed

if 'is' in str2.split(): # 'is' in ['This', 'is', 'a', 'string']
    print(str2) # printed

Answer 2

使用正则表达式的单词边界也可以

import re

if re.findall(r'\bis\b', str1):
    print str1