John Machin wrote:
Dave Opstad wrote:
One of the functions in a C extension I'm writing needs to return a
tuple of integers, where the length of the tuple is only known at
runtime. I'm currently doing a loop calling PyInt_FromLong to make
the
integers,
What is the purpose of this first loop?
In what variable-length storage are you storing these (Python) integers
during this first loop? Something you created with (a) PyMem_Malloc (b)
malloc (c) alloca (d) your_own_malloc?
then PyTuple_New, and finally a loop calling PyTuple_SET_ITEM
to set the tuple's items. Whew.
Whew indeed.
Does anyone know of a simpler way? I can't use Py_BuildValue because
I
don't know at compile-time how many values there are going to be. And
there doesn't seem to be a PyTuple_FromArray() function.
If I'm overlooking something obvious, please clue me in!
1. Determine the length of the required tuple; this may need a loop,
but only to _count_ the number of C longs that you have.
2. Use PyTuple_New.
3. Loop to fill the tuple, using PyInt_FromLong and PyTuple_SetItem.
Much later, after thoroughly testing your code, gingerly change
PyTuple_SetItem to PyTuple_SET_ITEM. Benchmark the difference. Is it
anywhere near what you saved by cutting out the store_in_temp_array
thing in the first loop?
Shouldn't something like this (uncompiled) do what you want?
- Dave
PyObject *PyTuple_FromArray(int *values, int num_values)
{
PyObject *tuple;
int i;
tuple = PyTuple_New(num_values);
if (tuple == NULL)
return NULL;
for (i = 0; i < num_values; i++) {
PyObject *obj;
obj = PyInt_FromLong(value[i]);
if (obj == NULL
|| PyTuple_SetItem(tuple, i, obj) != 0) {
Py_DECREF(tuple);
return NULL;
}
}
return tuple;
}
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