SyntaxError: Non-ASCII character '\\xa3' in file when function returns '£'

Question

Say I have a function:

def NewFunction():
    return '£'

I want to print some stuff with a pound sign in front of it and it prints an error when I try to run this program, this error message is displayed:

SyntaxError: Non-ASCII character '\xa3' in file 'blah' but no encoding declared;
see http://www.python.org/peps/pep-0263.html for details

Can anyone inform me how I can include a pound sign in my return function? I'm basically using it in a class and it's within the '__str__' part that the pound sign is included.

Answer 1

I'd recommend reading that PEP the error gives you. The problem is that your code is trying to use the ASCII encoding, but the pound symbol is not an ASCII character. Try using UTF-8 encoding. You can start by putting # -*- coding: utf-8 -*- at the top of your .py file. To get more advanced, you can also define encodings on a string by string basis in your code. However, if you are trying to put the pound sign literal in to your code, you'll need an encoding that supports it for the entire file.

Answer 2

Adding the following two line sat the top of my .py script worked for me (first line was necessary):

#!/usr/bin/env python
# -*- coding: utf-8 -*- 

Answer 3

First add the # -*- coding: utf-8 -*- line to the beginning of the file and then use u'foo' for all your non-ASCII unicode data:

def NewFunction():
    return u'£'

or use the magic available since Python 2.6 to make it automatic:

from __future__ import unicode_literals

Answer 4

The error message tells you exactly what's wrong. The Python interpreter needs to know the encoding of the non-ASCII character.

If you want to return U+00A3 then you can say

return u'\u00a3'

which represents this character in pure ASCII by way of a Unicode escape sequence. If you want to return a byte string containing the literal byte 0xA3, that's

return b'\xa3'

(where in Python 2 the b is implicit; but explicit is better than implicit).

The linked PEP in the error message instructs you exactly how to tell Python "this file is not pure ASCII; here's the encoding I'm using". If the encoding is UTF-8, that would be

# coding=utf-8

or the Emacs-compatible

# -*- encoding: utf-8 -*-

If you don't know which encoding your editor uses to save this file, examine it with something like a hex editor and some googling. The Stack Overflow character-encoding tag has a tag info page with more information and some troubleshooting tips.

In so many words, outside of the 7-bit ASCII range (0x00-0x7F), Python can't and mustn't guess what string a sequence of bytes represents. https://tripleee.github.io/8bit#a3 shows 21 possible interpretations for the byte 0xA3 and that's only from the legacy 8-bit encodings; but it could also very well be the first byte of a multi-byte encoding. But in fact, I would guess you are actually using Latin-1, so you should have

# coding: latin-1

as the first or second line of your source file. Anyway, without knowledge of which character the byte is supposed to represent, a human would not be able to guess this, either.