David M. Cotter, 03.08.2013 02:55:
> I'd like to be able to use PyArg_ParseTuple() in a generic way.
>
> for example, i'd like to have all commands start with 1 integer parameter,
> and this "commandID" will inform me of what parameters come next (via LUT).
>
> knowing that i can then call ParseTuple again with the proper parameters.
>
> like this:
>
> if (PyArg_ParseTuple(args, "i|", &commandID)) {
>
> switch (commandID) {
>
> case cmd_with_str: {
> const char *strZ = NULL;
>
> if (PyArg_ParseTuple(args, "is", &commandID, &strZ)) {
> // do something with string
> }
> break;
> }
>
> case cmd_with_float: {
> float valF = -1;
>
> if (PyArg_ParseTuple(args, "if", &commandID, &valF)) {
> // do something with float
> }
> break;
> }
> }
> }
>
> is there a way to achieve this? the "i|" at the start is not working
If you're willing to switch to Cython, here's an (untested) example:
cdef enum:
cmd_with_str = 1
cmd_with_float = 2
cdef int command_id = args[0]
if command_id == cmd_with_str:
str_z = args[1] # it's an object, so use it as such
print(str_z)
elif command_id == cmd_with_float:
val_f = <float>args[1] # converting to C float here
...
else:
raise ValueError("unknown command")
Two comments:
1) you can obviously do the same in C, by writing a bit more code. It would
likely be a lot slower, though, and you'd have to take care of error
handling etc.
2) you might want to rethink your design as this is a rather unpythonic
API. Although it depends on who (or what) you are expecting to use it.
Stefan
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