[Python-Dev] Smoothing the transition from Python 2 to 3 (original) (raw)

Paul Moore p.f.moore at gmail.com
Fri Jun 10 11:14:45 EDT 2016

On 10 June 2016 at 15:09, 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 is very nice. But...

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.

If you're fixing encoding errors at the point they occur, rather than looking at the high-level design of the program's handling of textual and bytestring data, you're likely to end up in a bit of a mess no matter how you locate the issues. Most likely because at the point in the code where the warning occurs, you no longer know what the correct encoding to use should be.

But absolutely, anything that gives extra information about where the encoding hotspots are in your code is of value. Paul

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