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

[Cody Piersall]

> 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.

This is nice because you can get in "fix my encoding errors" mode for
more than just one traceback at a time; the new method would be to run
the program, look at the millions of bytes/str errors, and fix
everything that showed up in this round at once.  That seems like a
big win for productivity to me.

Cody