Paul McGuire Paul McGuire - 9 months ago 45
Python Question

Why is '\x' invalid in Python?

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
\t - 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?

Answer Source

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)


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.