[Python-ideas] format specifier for "not bytes"

Mathias Panzenböck grosser.meister.morti at gmx.net
Thu Aug 30 00:30:58 CEST 2012

On 08/27/2012 04:34 PM, Barry Warsaw wrote:
> On Aug 25, 2012, at 09:16 AM, Nick Coghlan wrote:
>> A couple of people at PyCon Au mentioned running into this kind of issue
>> with Python 3. It relates to the fact that:
>> 1. String formatting is *coercive* by default
>> 2. Absolutely everything, including bytes objects can be coerced to a
>> string, due to the repr() fallback
>> So it's relatively easy to miss a decode or encode operation, and end up
>> interpolating an unwanted "b" prefix and some quotes.
>> For existing versions, I think the easiest answer is to craft a regex that
>> matches bytes object repr's and advise people to check that it *doesn’t*
>> match their formatted strings in their unit tests.
>> For 3.4+ a non-coercive string interpolation format code may be desirable.
> Or maybe just one that calls __str__ without a __repr__ fallback?

 >>> b'a'.__str__()

__str__ still returns the bytes literal representation.

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