Where does this come from: -*- coding: utf-8 -*-

Posted on

Question :

Where does this come from: -*- coding: utf-8 -*-

Python recognizes the following as instruction which defines file’s encoding:

# -*- coding: utf-8 -*-

I definitely saw this kind of instructions before (-*- var: value -*-). Where does it come from? What is the full specification, e.g. can the value include spaces, special symbols, newlines, even -*- itself?

My program will be writing plain text files and I’d like to include some metadata in them using this format.

Answer #1:

This way of specifying the encoding of a Python file comes from PEP 0263 – Defining Python Source Code Encodings.

It is also recognized by GNU Emacs (see Python Language Reference, 2.1.4 Encoding declarations), though I don’t know if it was the first program to use that syntax.

Answered By: Andrea Spadaccini

Answer #2:

# -*- coding: utf-8 -*- is a Python 2 thing. In Python 3+, the default encoding of source files is already UTF-8 and that line is useless.

See: Should I use encoding declaration in Python 3?

pyupgrade is a tool you can run on your code to remove those comments and other no-longer-useful leftovers from Python 2, like having all your classes inherit from object.

Answered By: Boris

Answer #3:

This is so called file local variables, that are understood by Emacs and set correspondingly. See corresponding section in Emacs manual – you can define them either in header or in footer of file

Answered By: Alex Ott

Answer #4:

In PyCharm, I’d leave it out. It turns off the UTF-8 indicator at the bottom with a warning that the encoding is hard-coded. Don’t think you need the PyCharm comment mentioned above.

Answered By: cwp393

Leave a Reply

Your email address will not be published. Required fields are marked *