在字符串文字前加“r"有什么作用?意思是? [英] What does preceding a string literal with "r" mean?

问题描述

我第一次看到它用于跨多行构建正则表达式作为 re.compile() 的方法参数，所以我假设 r 代表 RegEx.

I first saw it used in building regular expressions across multiple lines as a method argument to re.compile(), so I assumed that r stands for RegEx.

例如:

regex = re.compile(
    r'^[A-Z]'
    r'[A-Z0-9-]'
    r'[A-Z]$', re.IGNORECASE
)

那么在这种情况下 r 是什么意思?为什么我们需要它?

So what does r mean in this case? Why do we need it?

推荐答案

r 表示字符串将被视为原始字符串，这意味着所有转义码都将被忽略.

The r means that the string is to be treated as a raw string, which means all escape codes will be ignored.

举个例子:

' ' 将被视为换行符，而 r' ' 将被视为 后面的字符通过 n.

' ' will be treated as a newline character, while r' ' will be treated as the characters followed by n.

当存在 'r' 或 'R' 前缀时，反斜杠后面的字符是包含在字符串中而没有更改，并且所有反斜杠都留在细绳.例如，字符串文字 r" " 由两个字符:反斜杠和小写 'n'.字符串引号可以是用反斜杠转义，但是反斜杠保留在字符串中；为了例如，r""" 是一个有效的字符串由两个字符组成的字面量:一个反斜杠和一个双引号；r""不是有效的字符串文字(即使是原始字符串不能以奇数结尾反斜杠).具体来说，一个原始的字符串不能以单个结尾反斜杠(因为反斜杠会转义以下引号字符).另请注意，单个反斜杠后跟换行符被解释作为这两个字符的一部分字符串，而不是作为换行符.

When an 'r' or 'R' prefix is present, a character following a backslash is included in the string without change, and all backslashes are left in the string. For example, the string literal r" " consists of two characters: a backslash and a lowercase 'n'. String quotes can be escaped with a backslash, but the backslash remains in the string; for example, r""" is a valid string literal consisting of two characters: a backslash and a double quote; r"" is not a valid string literal (even a raw string cannot end in an odd number of backslashes). Specifically, a raw string cannot end in a single backslash (since the backslash would escape the following quote character). Note also that a single backslash followed by a newline is interpreted as those two characters as part of the string, not as a line continuation.

来源:Python 字符串文字

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