Correct way to define Python source code encoding

Question

PEP 263 defines how to declare Python source code encoding.

Normally, the first 2 lines of a Python file should start with:

#!/usr/bin/python
# -*- coding: <encoding name> -*-

But I have seen a lot of files starting with:

#!/usr/bin/python
# -*- encoding: <encoding name> -*-

=> encoding instead of coding.

So what is the correct way of declaring the file encoding?

Is encoding permitted because the regex used is lazy? Or is it just another form of declaring the file encoding?

I'm asking this question because the PEP does not talk about encoding, it just talks about coding.

Answer 1

Check the docs here:

"If a comment in the first or second line of the Python script matches the regular expression coding[=:]\s*([-\w.]+), this comment is processed as an encoding declaration"

"The recommended forms of this expression are

# -*- coding: <encoding-name> -*-

which is recognized also by GNU Emacs, and

# vim:fileencoding=<encoding-name>

which is recognized by Bram Moolenaar’s VIM."

So, you can put pretty much anything before the "coding" part, but stick to "coding" (with no prefix) if you want to be 100% python-docs-recommendation-compatible.

More specifically, you need to use whatever is recognized by Python and the specific editing software you use (if it needs/accepts anything at all). E.g. the coding form is recognized (out of the box) by GNU Emacs but not Vim (yes, without a universal agreement, it's essentially a turf war).

Answer 2

Just copy paste below statement on the top of your program.It will solve character encoding problems

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

Answer 3

PEP 263:

the first or second line must match the regular expression "coding[:=]\s*([-\w.]+)"

So, "encoding: UTF-8" matches.

PEP provides some examples:

#!/usr/bin/python
# vim: set fileencoding=<encoding name> :

 

# This Python file uses the following encoding: utf-8
import os, sys

Answer 4

As of today — June 2018

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PEP 263 itself mentions the regex it follows:

To define a source code encoding, a magic comment must be placed into the source files either as first or second line in the file, such as:

# coding=<encoding name>

or (using formats recognized by popular editors):

#!/usr/bin/python
# -*- coding: <encoding name> -*-

or:

#!/usr/bin/python
# vim: set fileencoding=<encoding name> : 

More precisely, the first or second line must match the following regular expression:

^[ \t\f]*#.*?coding[:=][ \t]*([-_.a-zA-Z0-9]+)

So, as already summed up by other answers, it'll match coding with any prefix, but if you'd like to be as PEP-compliant as it gets (even though, as far as I can tell, using encoding instead of coding does not violate PEP 263 in any way) — stick with 'plain' coding, with no prefixes.

Answer 5

If I'm not mistaken, the original proposal for source file encodings was to use a regular expression for the first couple of lines, which would allow both.

I think the regex was something along the lines of coding: followed by something.

I found this: http://www.python.org/dev/peps/pep-0263/ Which is the original proposal, but I can't seem to find the final spec stating exactly what they did.

I've certainly used encoding: to great effect, so obviously that works.

Try changing to something completely different, like duhcoding: ... to see if that works just as well.

Answer 6

I suspect it is similar to Ruby - either method is okay.

This is largely because different text editors use different methods (ie, these two) of marking encoding.

With Ruby, as long as the first, or second if there is a shebang line contains a string that matches:

coding: encoding-name

and ignoring any whitespace and other fluff on those lines. (It can often be a = instead of :, too).