GSoC Week #3

I was moving back to Singapore this week, so it is pretty late for this post to come out. However, now I have settled down and got some time to sit on the front of my laptop to work on Cython again. Yeah!

Last week I have attempted ticket #69 emulate Python 3 print() function in Py2 <2.6. With some research, I figured out that the print() function could be implemented easily in Python/Cython code, by putting these code in the head of a module during compiling:

from __future__ import print_function

if __import__('sys').version_info < (2,6):
    def print(*args, sep=' ', end='p\n', file=None):
        import sys
        if file is None:
            file=sys.stdout
        sep = str(sep)
        end = str(end)
        file.write(sep.join([str(x) for x in args]))
        file.write(end)
        return None

The about code is actually invalid for Python <2.6 since they don’t support the print_function future directive. However, it is valid in Cython no matter which version of Python you are using. This is because Cython compiles these code to extension module, thus circumvented the Python parser. Finally, Python will not complain if you define a function named “print” in extension module.

But function def inside a if statement is not working yet for Cython. So we need to implement function definition in control structure (ticket #87). This meant to treat function definition as assignment, as what pure Python code do. Cython already doing so in some case, such as for closure. So what I need to do is to enable it. Seems not too hard.

After some hacking, it starts to work, but cannot pass some corner case. I might be going on the wrong way, i.e., should not do this kind of monkey patching against the test failures, but to give a complete solution based on deep understanding of the code base? Hmm.. finally I decide to put it aside. Maybe I can figure out a better solution later when I got a better understanding of Cython code base.

I’d like to start work on relative import then. Meanwhile it should be the time to call the community to review the patches I produced. So I can revise them and learn more.