python invalid_为什么'\x'在Python中无效？

I was experimenting with '\' characters, using '\a\b\c...' just to enumerate for myself which characters Python interprets as control characters, and to what. Here's what I found:

\a - BELL

\b - BACKSPACE

\f - FORMFEED

\n - LINEFEED

\r - RETURN

\t - TAB

\v - VERTICAL TAB

Most of the other characters I tried, '\g', '\s', etc. just evaluate to the 2-character string of a backslash and the given character. I understand this is intentional, and makes sense to me.

But '\x' is a problem. When my script reaches this source line:

val = "\x"

I get:

ValueError: invalid \x escape

What is so special about '\x'? Why is it treated differently from the other non-escaped characters?

解决方案

There is a table listing all the escape codes and their meanings in the documentation.

Escape Sequence Meaning Notes

\xhh Character with hex value hh (4,5)

Notes:

4. Unlike in Standard C, exactly two hex digits are required.

5. In a string literal, hexadecimal and octal escapes denote the byte

with the given value; it is not necessary that the byte encodes a character

in the source character set. In a Unicode literal, these escapes denote a

Unicode character with the given value.