python中的r'string'和普通的'string'有什么区别？

Question

python中的r字符串（r'foobar'）和普通字符串（'foobar'）有什么区别？r'string'是正则表达式字符串吗？在

我尝试了以下操作，但对我的正则表达式匹配没有任何影响：

>>> import re
>>> n = 3
>>> rgx = '(?=('+'\S'*n+'))'
>>> x = 'foobar'
>>> re.findall(rgx,x)
['foo', 'oob', 'oba', 'bar']
>>>
>>> rgx2 = r'(?=('+'\S'*n+'))'
>>> re.findall(rgx2,x)
['foo', 'oob', 'oba', 'bar']
>>>
>>> rgx3 = r'(?=(\S\S\S))'
>>> re.findall(rgx3,x)
['foo', 'oob', 'oba', 'bar']

Answer 1

在使用反斜杠转义符的情况下，这种区别将变得明显：

>>> s="foobar"
>>> import re
>>> re.sub('(o)\1', '', s)     # Using the backreference has no effect here as it's interpreted as a literal escaped 1
'foobar'
>>> re.sub(r'(o)\1', '', s)    # Using the backreference works!
'fbar'
>>> re.sub('(o)\\1', '', s)    # You need to escape the backslash here
'fbar'

引自String literal：

A few languages provide a method of specifying that a literal is to be processed without any language-specific interpretation. This avoids the need for escaping, and yields more legible strings.

您可能还想引用Lexical Analysis。在

Answer 2

r不表示“regex string”；它的意思是“raw string”。根据the docs：

String literals may optionally be prefixed with a letter 'r' or 'R'; such strings are called raw strings and use different rules for interpreting backslash escape sequences.