[Python-Dev] Smoothing the transition from Python 2 to 3

[Nick Coghlan]

On 10 June 2016 at 07:09, Cody Piersall <cody.piersall at gmail.com> wrote:
>> One problem is that the str literals should be bytes
>> literals.  Comparison with None needs to be avoided.
>>
>> With Python 2 code runs successfully.  With Python 3 the code
>> crashes with a traceback.  With my modified Python 3.6, the code
>> runs successfully but generates the following warnings:
>>
>>     test.py:13: DeprecationWarning: encoding bytes to str
>>       output.write('%d:' % len(s))
>>     test.py:14: DeprecationWarning: encoding bytes to str
>>       output.write(s)
>>     test.py:15: DeprecationWarning: encoding bytes to str
>>       output.write(',')
>>     test.py:5: DeprecationWarning: encoding bytes to str
>>       if c == ':':
>>     test.py:9: DeprecationWarning: encoding bytes to str
>>       size += c
>>     test.py:24: DeprecationWarning: encoding bytes to str
>>       data = data + s
>>     test.py:26: DeprecationWarning: encoding bytes to str
>>       if input.read(1) != ',':
>>     test.py:31: DeprecationWarning: default compare is depreciated
>>       if a > 0:
>>
>
> This seems _very_ useful; I'm surprised that other people don't think
> so too.  Currently, the easiest way to find bytes/str errors in a big
> application is by running the program, finding where it crashes,
> fixing that one line (or hopefully wherever the data entered the
> system if you can find it), and repeating the process.

It could be very interesting to add an "ascii-warn" codec to Python
2.7, and then set that as the default encoding when the -3 flag is
set. The expressed lack of interest has been in the idea of
recommending people use an alternate interpreter build (which has
nothing to do with the usefulness of the added warnings, and
everything to do with the logistics of distributing and adopting
alternate runtimes), rather than in the concept of improving the
available runtime compatibility warnings.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia