[Python-Dev] Include datetime.py in stdlib or not? (original) (raw)

Terry Reedy tjreedy at udel.edu
Thu Jul 8 00:17:33 CEST 2010

On 7/7/2010 3:32 PM, Brett Cannon wrote:

That's the idea. We already have contributors from the various VMs who has commit privileges, but they all work in their own repos for convenience. My hope is that if we break the stdlib out into its own repository that people simply pull in then other VM contributors will work directly off of the stdlib repo instead of their own, magnifying the usefulness of their work.

I was wondering if you had more than 'hope', but thinking about it now, I think it premature to ask for commitments. Once a Python3 stdlib hg subrepository is set up and running, the logic of joining in should be obvious -- or not.

I am now seeing that a more complete common Python-level test suite is also important. Being able to move Python code, that only uses the stdlibk,between implementations and have it just work would be good for all of them.

3. What version of Python would be allowed for use in the stdlib? I would like the stdlib for 3.x to be able to use 3.x code. This would be only a minor concern for CPython as long as 2.7 is maintained, but a major concern for the other implementation currently 'stuck' in 2.x only. A good 3to2 would be needed. This will only affect py3k.

Good. The Python3 stdlib should gradually become modern Python3 code. (An example archaism -- the use in difflib of dicts with arbitrary values used as sets -- which I plan to fix.)

I generally favor having Python versions of modules available. My current post on difflib.SequenceMatcher is based on experiments with an altered version. I copied difflib.py to my test directory, renamed it diff2lib.py, so I could import both versions, found and edited the appropriate method, and off I went. If difflib were in C, my post would have been based on speculation about how a fixed version would operate, rather than on data.

The effect upon CPython would be the extension modules become just performance improvements, nothing more (unless they have to be in C as in the case for sqlite3).

As pre- and jit compilation improve, the need for hand-coded C will go down. For instance, annotate (in a branch, not trunk) and compile with Cython.

4. Does not ctypes make it possible to replace a method of a Python-coded class with a faster C version, with something like try: connect to methods.dll check that function xyx exists replace Someclass.xyy with ctypes wrapper except: pass For instance, the SequenceMatcher heuristic was added to speedup the matching process that I believe is encapsulated in one O(n**2) or so bottleneck method. I believe most everything else is O(n) bookkeeping.

There is no need to go that far. All one needs to do is structure the extension code such that when the extension module is imported, it overrides key objects in the Python version.

Is it possible to replace a python-coded function in a python-coded class with a C-coded function? I had the impression from the issue discussion that one would have to recode the entire class, even if only a single method really needed it.

Using ctypes is just added complexity.

Only to be used if easier than extra C coding.

-- Terry Jan Reedy

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