Encoding of Python 2 string literals

[dieter]

Steven D'Aprano <steve at pearwood.info> writes:
> On Wed, 22 Jul 2015 08:17 pm, anatoly techtonik wrote:
>> Is there a way to know encoding of string (bytes) literal
>> defined in source file? For example, given that source:
>> 
>>     # -*- coding: utf-8 -*-
>>     from library import Entry
>>     Entry("текст")
>> 
>> Is there any way for Entry() constructor to know that
>> string "текст" passed into it is the utf-8 string?
> ...
> The right way to deal with this is to use an actual Unicode string:
>
> Entry(u"текст")
>
> and make sure that the file is saved using UTF-8, as the encoding cookie
> says.

In order to follow this recommendation, is there an easy way to
learn about the "encoding cookie"'s value -- rather than parsing
the first two lines of the source file (which may not always be available).