python的print r''

Question

python小白一枚，在看文档的时候，说到print r'' 表示''内部的字符串默认不转义,

请问 为什么会报错？

//    会报错     EOL while scanning string literal
print r'\\\\\'

//    不报错
print r'\\\\\\'

版本：python 2.7

Answer 1

这是Python标准中的规定。

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"\n" 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.