On 14.04.2012 20:12, Brett Cannon wrote:
My multi-year project -- started in 2006 according to my blog -- to rewrite
import in pure Python and then bootstrap it into CPython as *the* implementation
of __import__() is finally over (mostly)! Hopefully I didn't break too much code
in the process. =)
Now this is "mostly" finished because the single incompatibility that importlib
has is that it doesn't check the Windows registry for paths to search since I
lack a Windows installation to develop and test on. If someone can tackle that
issue that would be greatly appreciated (http://bugs.python.org/issue14578).
Next up is how to maintain/develop for all of this. So the Makefile will
regenerate Python/importlib.h whenever Lib/importlib/_bootstrap.py or
Python/freeze_importlib.py changes. So if you make a change to importlib make
sure to get it working and tested before running 'make' again else you will
generate a bad frozen importlib (if you do mess up you can also revert the
changes to importlib.h and re-run make; a perk to having importlib.h checked
in). Otherwise keep in mind that you can't use any module that isn't a builtin
(sys.builtin_module_names) in importlib._bootstrap since you can't import
something w/o import working. =)
We've just now talked on IRC about this regeneration. Since both files --
_bootstrap.py and importlib.h -- are checked in, a make run can try to re-
generate importlib.h. This depends on the timestamps of the two files, which I
don't think Mercurial makes any guarantees about.
We have other instances of this (e.g. the Objects/typeslots.inc file is
generated and checked in), but in the case of importlib, we have to use the
./python binary for freezing to avoid bytecode incompatibilities, which
obviously is a problem if ./python isn't built yet.
And the only outstanding point of contention in all of this is that some people
don't like having freeze_importlib.py in Python/ and instead want it in Tools/.
I didn't leave it in Tools/ as I have always viewed that Python should build w/o
the Tools directory, but maybe the Linux distros actually ship with it and thus
this is an unneeded worry. Plus the scripts to generate the AST are in Parser so
there is precedent for what I have done.
I would have no objections to Python/. There is also e.g. Objects/typeslots.py.
Georg
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