[Python-Dev] What does a double coding cookie mean?

Brett Cannon brett at python.org
Tue Mar 15 17:04:57 EDT 2016

On Tue, 15 Mar 2016 at 13:31 Guido van Rossum <guido at python.org> wrote:

> I came across a file that had two different coding cookies -- one on
> the first line and one on the second. CPython uses the first, but mypy
> happens to use the second. I couldn't find anything in the spec or
> docs ruling out the second interpretation. Does anyone have a
> suggestion (apart from following CPython)?
> Reference: https://github.com/python/mypy/issues/1281

I think the spirit of PEP 263 is for the first specified encoding to win as
the support of two lines is to support shebangs and not multiple encodings
:) . I also think the fact that tokenize.detect_encoding()
doesn't automatically read two lines from its input also suggests the
intent is "first encoding wins" (and that is the semantics of the function).
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