Both string and bytes literals may optionally be prefixed with a letter ‘ r ’ or ‘ R ’; such constructs are called raw string literals and raw bytes literals respectively and treat backslashes as literal characters. As a result, in raw string literals, escape sequences are not treated specially:
>>> r'\d{4}-\d{2}-\d{2}''\\d{4}-\\d{2}-\\d{2}'
Even in a raw literal, quotes can be escaped with a backslash, but the backslash remains in the result; 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 literal 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 literal, not as a line continuation.