[Python-Dev] Interop between datetime and mxDateTime (original) (raw)

Tim Peters tim.one@comcast.net
Mon, 13 Jan 2003 11:16:23 -0500

[M.-A. Lemburg]

I'd like to make mxDateTime and datetime in Python 2.3 cooperate.

Cool! Good luck .

Looking at the datetime.h file, it seems that the C API isn't all that fleshed out yet. Will this happen before 2.3b1 ?

There are no plans to expand the C API. Macros are provided for efficient field extraction; all objects here are immutable so there are no macros for changing fields; anything else needed has to go thru PyObject_CallMethod on an existing datetime object, or (for construction) calling the type object.

Related to this: I wonder why datetime is not a normal Python object which lives in Objects/ ?!

Didn't fit there. Like, e.g., arraymodule.c and mmapmodule.c, it implements a module the user needs to import explicitly (as well as supplying new object types). Nothing in Objects is like that (they don't implement modules).

Finally, the datetime objects don't seem to provide any means of letting binary operations with other types succeed. Coercion or mixed type operations are not implemented. When will this happen ?

Coercion is out of favor. Binary datetime methods generally return NotImplemented when they don't know how to handle an operation themself. In that case, Python then asks "the other" object to try the operation. If that also returns NotImplemented, then Python complains.

date.today() + 12 Traceback (most recent call last): File "", line 1, in ? TypeError: unsupported operand type(s) for +: 'datetime.date' and 'int'

That outcome means that date and int both got a crack at it, and both returned NotImplemented.

Comparison is an exception to this: in order to stop comparison from falling back to the default compare-by-object-address, datetime comparison operators explictly raise TypeError when they don't know what to do. Offhand that seems hard (perhaps impossible) to worm around.