[Pyrex] Question about +=, -=, *=, etc.

[Phillip J. Eby]

At 10:00 AM 6/3/04 -0600, Fernando Perez wrote:
>I'd really like to use Pyrex for my
>code, especially now that I see there are good examples of how to deal with
>Numeric arrays.
>
>However, the critical path of my codes relies heavily on things like:
>
>for i in long_list:
>         my_array += some_function(i)
>
>For code like this, which is performance-critical, pyrex sounds great.  I
>can't write the whole thing in Fortran, because there's key reliance on python
>dicts for many things in there.


Try this as a simple workaround:

     cdef extern from "Python.h":
         object PyNumber_InPlaceAdd(object o1, object o2)

     for i in long_list:
         my_array = PyNumber_InPlaceAdd(my_array,some_function(i))

This is effectively the code that a += operator would generate.

In general, if you're looking to improve Python performance via Pyrex, it's 
important to know what functions are available in the Python/C API, as 
calling these functions directly can, under the right circumstances, yield 
further performance boosts over "naive" Pyrex code.