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

[M.-A. Lemburg]

On 16.03.2016 01:28, Guido van Rossum wrote:
> I agree that the spirit of the PEP is to stop at the first coding
> cookie found. Would it be okay if I updated the PEP to clarify this?
> I'll definitely also update the docs.

+1

The only reason to read up to two lines was to address the use of
the shebang on Unix, not to be able to define two competing
source code encodings :-)

> On Tue, Mar 15, 2016 at 2:04 PM, Brett Cannon <brett at python.org> wrote:
>>
>>
>> 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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