删除单个换行符但保留多个换行符的最佳方法 [英] Best way of removing single newlines but keeping multiple newlines

问题描述

从字符串中删除单个换行符但保留多个换行符的最pythonic 的方法是什么?

如在

"foo\n\nbar\none\n\rtwo\rthree\n\n\nhello"

变成

"foo\n\nbar 一二三\n\n\nhello"

我正在考虑使用 splitlines()，然后用 "\n" 替换空行，然后再次连接所有内容，但我怀疑有更好/更简单的方法.也许使用正则表达式?

解决方案

>>>re.sub('(?

这会查找 \r?\n 或 \n?\r 并使用后视和前瞻断言来防止任何一侧出现换行符.

就其价值而言，在野外发现了三种类型的行尾:

1. \n 在 Linux、Mac OS X 和其他 Unices 上
2. \r\n 在 Windows 和 HTTP 协议中
3. \r 在 Mac OS 9 及更早版本上

前两个是迄今为止最常见的.如果您想将可能性限制为仅这三个，您可以这样做:

<预><代码>>>>re.sub('(?

当然，如果你不关心 Mac 的行尾，那就去掉 |\r，这种情况很少见.

What would be the most pythonic way of removing single newlines but keeping multiple newlines from a string?

As in

"foo\n\nbar\none\n\rtwo\rthree\n\n\nhello"

turning into

"foo\n\nbar one two three\n\n\nhello"

I was thinking about using splitlines(), then replacing empty lines by "\n" and then concatenating everything back again, but I suspect there is a better/simpler way. Maybe using regexes?

解决方案

>>> re.sub('(?<![\r\n])(\r?\n|\n?\r)(?![\r\n])', ' ', s)
'foo\n\nbar one two three\n\n\nhello'

This looks for \r?\n or \n?\r and uses lookbehind and lookahead assertions to prevent there from being a newline on either side.

For what it's worth, there are three types of line endings found in the wild:

1. \n on Linux, Mac OS X, and other Unices
2. \r\n on Windows, and in the HTTP protocol
3. \r on Mac OS 9 and earlier

The first two are by far the most common. If you want to limit the possibilities to just those three, you could do:

>>> re.sub('(?<![\r\n])(\r?\n|\r)(?![\r\n])', ' ', s)
'foo\n\nbar one two three\n\n\nhello'

And of course, get rid of the |\r if you don't care about Mac line endings, which are rare.

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