如何替换 Python 中第一次出现的正则表达式？
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How to replace the first occurrence of a regular expression in Python?
提问by girish
I want to replace just the first occurrence of a regular expression in a string. Is there a convenient way to do this?
我只想替换字符串中第一次出现的正则表达式。有没有方便的方法来做到这一点？
回答by Nick T
Specify the countargument in re.sub(pattern, repl, string[, count, flags])
指定count参数re.sub(pattern, repl, string[, count, flags])
The optional argument count is the maximum number of pattern occurrences to be replaced; count must be a non-negative integer. If omitted or zero, all occurrences will be replaced.
可选参数 count 是要替换的模式出现的最大次数；count 必须是非负整数。如果省略或为零，则将替换所有出现的内容。
回答by eldarerathis
re.sub()has a countparameter that indicates how many substitutions to perform. You can just set that to 1:
re.sub()有一个count参数指示要执行多少次替换。您可以将其设置为 1：
>>> s = "foo foo foofoo foo"
>>> re.sub("foo", "bar", s, 1)
'bar foo foofoo foo'
>>> s = "baz baz foo baz foo baz"
>>> re.sub("foo", "bar", s, 1)
'baz baz bar baz foo baz'
Edit: And a version with a compiled SRE object:
编辑：以及带有编译的 SRE 对象的版本：
>>> s = "baz baz foo baz foo baz"
>>> r = re.compile("foo")
>>> r.sub("bar", s, 1)
'baz baz bar baz foo baz'
