python – 替换第一个出现在字符串中的所有匹配项

发布时间：2020-12-20 13:00:31 所属栏目：Python 来源：网络整理

导读：鉴于字符串： X did something. X found it to be good,and so X went home. 我想用Y替换所有出现的X但第一个出现,这样输出字符串看起来像： X did something. Y found it to be good,and so Y went home. 我尝试了很多正则表达式模式(基于https://vi.stacke

鉴于字符串：

X did something. X found it to be good,and so X went home.

我想用Y替换所有出现的X但第一个出现,这样输出字符串看起来像：

X did something. Y found it to be good,and so Y went home.

我尝试了很多正则表达式模式(基于https://vi.stackexchange.com/questions/10905/substitution-how-to-ignore-the-nth-first-occurrences-of-a-pattern),但未能用Python实现

解决方法

str.partition在分隔符,分隔符本身和后面的部分之前将字符串拆分为部分,如果分隔符不存在,则将字符串和两个空字符串分割.归结为：

s = 'X did something. X found it to be good,and so X went home.'
before,first,after = s.partition('X')
result = before + first + after.replace('X','Y')

（编辑：李大同）

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