Make the entire codebase Python3 compatible without using 2to3

[cpcloud]

• deprecate iterkv

[jtratner]

Could try running https://github.com/mitsuhiko/python-modernize on it. Actually, I'm going to do it now and see what happens.

[jtratner]

Check it - bunch of changes...worth thinking through https://github.com/jtratner/pandas/tree/python-modernize-it . Going to see what happens if we remove 2to3 as well...

Main thing are the xrange --> range changes. Maybe use from six.moves import xrange instead?

[jtratner]

aaannnd it has tons of errors to fix...

[jreback]

is there a way to essentially find all d these errors then fix them (by doing code changes) gradually
eg maybe certain types of errors at a time (doing xrange -> range pretty straightforward)

using a tool to find them but shouldn't have a dep for the actual changes

[cpcloud]

xrange to range will still need 2to3 since if you write range(3) in 2 then 2to3 will assume you mean [0,1,2] and it will rewrite it as list(range(3))

[cpcloud]

six does all of the checking for you that would be needed to avoid 2to3, although you're right xrange -> range can just be redefined

[jtratner]

Yeah, that's what I'm doing. I'm just going fix by fix on this which makes it easier to do. Basically six converts everything to iterators and then you need to explicitly choose to convert things to lists.

[jtratner]

Right now I'm doing u"some string" --> six.u("some string"), etc.

[jreback]

ok
i would ship six with pandas (only 1 python file) and it encourages this

[cpcloud]

@jtratner after all ur prs pandas is going to be sparkling clean ❇️

[jtratner]

haha, frankly these fixes end up being great ways to learn the code base, because they break minor things / show up issues and then I can fix them 😄