[Numpy-discussion] numpy C API bugs?
David Ian Brown
dbrown at ucar.edu
Thu Mar 9 15:57:04 CST 2006
Hi Travis and NumPy developers,
I have recently been engaged in updating the PyNIO module
to work with the NumPy C API. It was originally coded using the
Numeric's C API.
In the process I have encountered what appear to me to be a couple of
bugs in the interface. They were relatively minor and not difficult
to work around, but you would probably like to know of them if you
In the NumPy version of arrayobject.h the macros PyArray_GETITEM and
are defined in way that does not work. Here is the GETITEM macro:
#define PyArray_GETITEM(obj,itemptr) \
((char *)itemptr, \
When I try to use this macro in my code I get a compile error, because
'getitem' is not a member of NumPy's
PyArray_Descr struct. Instead it is further nested within the struct
member 'PyArray_ArrFuncs *f'.
So, unless I misunderstand, the macro needs to access the 'getitem'
The other issue with 'getitem', apparently the actual method, not just
this macro, is that the 2 arguments are
ordered oppositely from what is stated in "Guide To NumPy", as well
as from the way this method was
implemented in Numeric. Notice in the macro (and in NumPy's
implementation), 'itemptr' is first and
the PyArrayObject pointer is second. The documentation and Numeric has
it the other way around.
I hope this is useful.
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