带有标志的 Python re.sub 不会替换所有出现的 [英] Python re.sub with a flag does not replace all occurrences

问题描述

Python 文档说:

<块引用>

re.MULTILINE:指定时，模式字符 '^' 匹配字符串的开头和每行的开头(紧跟在每个换行符之后)...默认情况下，'^' 仅匹配开头字符串...

那么当我得到以下意想不到的结果时发生了什么?

<预><代码>>>>进口重新>>>s = """//敏捷的棕色狐狸....//跳过了懒狗.""">>>re.sub('^//', '', s, re.MULTILINE)' 敏捷的棕色狐狸.\n//跳过了懒狗.'

解决方案

看re.sub:

re.sub(pattern, repl, string[, count, flags])

第四个参数是计数，您使用 re.MULTILINE(即 8)作为计数，而不是标志.

要么使用命名参数:

re.sub('^//', '', s, flags=re.MULTILINE)

或者先编译正则表达式:

re.sub(re.compile('^//', re.MULTILINE), '', s)

The Python docs say:

re.MULTILINE: When specified, the pattern character '^' matches at the beginning of the string and at the beginning of each line (immediately following each newline)... By default, '^' matches only at the beginning of the string...

So what's going on when I get the following unexpected result?

>>> import re
>>> s = """// The quick brown fox.
... // Jumped over the lazy dog."""
>>> re.sub('^//', '', s, re.MULTILINE)
' The quick brown fox.\n// Jumped over the lazy dog.'

解决方案

Look at the definition of re.sub:

re.sub(pattern, repl, string[, count, flags])

The 4th argument is the count, you are using re.MULTILINE (which is 8) as the count, not as a flag.

Either use a named argument:

re.sub('^//', '', s, flags=re.MULTILINE)

Or compile the regex first:

re.sub(re.compile('^//', re.MULTILINE), '', s)

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