extending python with array functions

[Janwillem]

I want to make numerical functions that can be called from python.
I am programming in pascal the last few decades so I had a look at
"python for delphi" (P4D). The demo09 gives as example add(a,b) using
integers and pyarg_parsetuple. That works!

However, I cannot figure out what to do when a, b and the result are
arrays (or matrices) of float (for i:=0 to high(a) do c[i]:=a[i]+b[i];
and then return c to python). Although from the ALGOL60 school and
always tried to keep far from pointers, I might also understand advise in C.

Please get me started e.g. by giving a simple example.
Many thanks,
Janwillem

[Marc 'BlackJack' Rintsch]

On Mon, 04 Feb 2008 20:56:02 -0200, Gabriel Genellina wrote:

- the array module http://docs.python.org/lib/module-array.html provides
homogeneuos arrays that may be more efficient for your application. arrays
don't have a special API, you have to import the module and use its
functions the same as one would do in pure Python.

There's one special thing about it: the `buffer_info()` method returns a
tuple with the memory address and length (in items) of the current
underlying buffer. Pretty useless information in Python but handy in
extensions that can directly access the "raw" memory.

To the OP: Since PythonÂ*2.5 the `ctypes` module is another way to
interface with "native" code in dynamic libraries from the standard
library.

Ciao,
Marc 'BlackJack' Rintsch

[Gabriel Genellina]

En Tue, 05 Feb 2008 05:28:33 -0200, Marc 'BlackJack' Rintsch
<bj****@gmx.netescribi�:

On Mon, 04 Feb 2008 20:56:02 -0200, Gabriel Genellina wrote:

>- the array module http://docs.python.org/lib/module-array.html provides
homogeneuos arrays that may be more efficient for your application.
arrays
don't have a special API, you have to import the module and use its
functions the same as one would do in pure Python.

There's one special thing about it: the `buffer_info()` method returns a
tuple with the memory address and length (in items) of the current
underlying buffer. Pretty useless information in Python but handy in
extensions that can directly access the "raw" memory.

Good to know! I didn't notice it the (only) time I had to use arrays from
C code.

--
Gabriel Genellina

[Janwillem]

Gabriel Genellina wrote:

En Tue, 05 Feb 2008 05:28:33 -0200, Marc 'BlackJack' Rintsch
<bj****@gmx.netescribi�:

>On Mon, 04 Feb 2008 20:56:02 -0200, Gabriel Genellina wrote:

>>- the array module http://docs.python.org/lib/module-array.html provides
homogeneuos arrays that may be more efficient for your application.
arrays
don't have a special API, you have to import the module and use its
functions the same as one would do in pure Python.

There's one special thing about it: the `buffer_info()` method returns a
tuple with the memory address and length (in items) of the current
underlying buffer. Pretty useless information in Python but handy in
extensions that can directly access the "raw" memory.

Good to know! I didn't notice it the (only) time I had to use arrays
from C code.

Thanks for the advice. I think I will read the cstype stuff because it
might mean that my calculation intensive functions (non-linear systems
and Monte Carlo stuff) can be kept unchanged ans stay compatible with
e.g. the Excel interfaces I have for them. My first attempt with
sum(i,j) was successful but sum(x,y) (FORTRAN typecast thinking) needs
apparently understanding ctypes.
Janwillem