ppython

For those still running 2.7 because migrating is too hard, consider using my "ppython" version (https://github.com/nascheme/ppython). It is a modified version of 3.6 with extra backwards compatibility features. After running your code through 2to3, it should mostly work with ppython. After fixing all the runtime warnings, your code should work with regular 3.6.

The implicit coercion between bytes and unicode was one of the biggest hurtles I ran into when porting a relatively large (30k+ lines) code base from Python 2 to 3. Also challenging was the change in comparisons (None no longer smaller than all types, TypeError when trying to order disjoint types). While this looks like an interesting hack, I can't see anyone seriously using it to backport code to Python 2.7. As I mentioned elsewhere, I created "ppython" to handle these two porting problems. The source code is on github: https://github.com/nascheme/ppython . If someone needs a Windows binary, I could build it if you ask politely. ;-) For my project, it has been a useful tool to speed up porting. Porting code is not trivial and there is huge amount of Python 2 out there. I wish more effort had been spent building tools to help portin

Interesting but I wonder when you would need a tool like that. I have something related, a fork of Python 3.6 that adds a bunch of backwards compatible behaviour so 2.7 code runs more easily, https://github.com/nascheme/ppython .

Porting Python code from version 2.x to 3.x is not a simple task. To help, I built a version of Python 3.6 that includes backwards compatibility features. Most important is the mixing of bytes and str objects and comparisons. For example, in vanilla Python 3: >>> b'foo' + 'bar' Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: can't concat bytes to str >>> None < 'hi' Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unorderable types: NoneType() < str() In my Python 3: >>> b'foo' + 'bar' sys:1: DeprecationWarning: encoding bytes to str 'foobar' >>> None < 'hi' __main__:1: DeprecationWarning: default compare is depreciated True Certain changes are easy to fix with code converters like 2to3. For example, changing print statements into fun

> what's happening to Python? Great things, IMHO. Now that the painful changes of 2 to 3 are done (or nearly so), recent releases have focused on incremental and steady progress. Take a look at the "What's New" documents: https://docs.python.org/3.6/whatsnew/3.6.html https://docs.python.org/3/whatsnew/3.5.html There is a lot of great stuff there without ripping up the world and breaking all your programs. For example, the new compact dict implementation in 3.6 is a great improvement. All Python programs can potentially benefit from the memory use reduction. Bug fixes and improvements to library code are great. The transition from 2.x to 3.x was not handled well. The core Python team should have focused much more on making transitioning code easier. Allowing code that can easily run in both 2.x and 3.x (with suitable shims like 'si

The unicode/bytes change it the most time consuming in my experience. Second comes the fact that you can't sort arbitrary types anymore and that None is no longer smaller than any other value. In order to ease porting, I've created a modified Python 3.6 interpreter that generates warnings in a lot of the cases that real Python 3 would generate an exception. See https://github.com/nascheme/ppython . The goal is to have a 2to3 script that generates something that will run, with warnings, under me modified Python. Once you fix all the warnings, your code should run correctly in Python 3.