09 February 2013

Python3 support by Nuitka is upcoming

This is kind of semi-interesting news for you Python3 lovers. My “Python compiler Nuitka” has been supporting the language somewhat, but in the next release it’s going to be complete.

Support for annotations, unicode variable names, keyword only arguments, starred assignments, exception chaining plus causes, and full support for new meta classes all have been added. So Python3.2 is covered now too and passing the test suite on about the same level as with Python2.6 and Python2.7 already.

I readied this while working on optimization, which is also seeing some progress, that I will report on another day. Plus it’s “available now on PyPI” too. At the time of this writing, there is pre-releases there, but after next release, there will only stable releases published.

My quick take on the Python3 that I saw:

Keyword Only Arguments

Now seriously. I didn’t miss that. And I am going to hate the extra effort it causes to implement argument parsing. And when I looked into default handling, I was just shocked:

def f( some_arg = function1(), *, some_key_arg = function2() )

What would you expect the evaluation order to be for defaults? I raised a CPython “bug report” about it. And I am kind of shocked this could be wrong.


def f( arg1 : c_types.c_int, arg2 : c_types.c_int ) -> c_types.c_long
   return arg1+arg2

That looks pretty promising. I had known about that already, and I guess, whatever “hints” idea, we come up with Nuitka, it should at least allow this notation. Unfortunately, evaluation order of annotations is not that great either. I would expected them to come first, but they come last. Coming last, they kind of come too late to accept do anything with defaults.

Unicode Variables

Now great. While it’s one step closer to “you can’t re-enter any identifier without copy&paste”, it is also a whole lot more consistent, if you come e.g. from German or French and need only a few extra letters. And there has to be at least one advantage to making everything unicode, right?

Exception Chaining

Gotta love that. Exception handlers are often subject to bit rot. They will themselves contain errors, when they are actually used, hiding the important thing that happened. No more. That’s great.

The exception causes on the other hand, might be useful, but I didn’t see them a lot yet. That’s probably because they are too new.

Starred Assigns

I was wondering already, why that didn’t work before.

a, *b = something()

Metaclass __prepare__

That’s great stuff. Wish somebody had thought about meta classes that way from the outset.


Yeah, big stuff. I love it. Also being able to write closure variables is great for consistency.


Nothing ground breaking. Nothing that makes me give up on Python2.7 yet, but a bunch of surprises. And for Nuitka, this also found bugs and corner cases, where things were not yet properly tested. The Python3 test suite, inspired the finding of some obscure compatibility problems for sure.

Overall, it’s possible to think of Python2 and Python3 as still the same language with only minor semantic differences. These can then be dealt with re-formulations into the simpler Python that Nuitka optimization deals with internally.

I for my part, am still missing the print statement. But well, now Python3 finds them when I accidentally check them in. So that’s kind of a feature for as long as I develop in Python2.6/2.7 language.

Now if one of you would help out with Python3.3, that would be great. It would be about the new dictionary implementation mostly. And maybe finding a proper re-formulation for “yield from” too.