[Numpy-discussion] fromfile() -- help!

Christopher Barker Chris.Barker@noaa....
Thu Jan 7 19:21:34 CST 2010


OK,

I'm trying to dig into the code and figure out how to get it to stop 
putting in zeros for missing data with fromfile()/fromstring() text reading.

It looks like the culprit is this, in arraytypes.c.src:


@fname@_scan(FILE *fp, @type@ *ip, void *NPY_UNUSED(ignore), 
PyArray_Descr *NPY_UNUSED(ignored))
{
     double result;
     int ret;

     ret = NumPyOS_ascii_ftolf(fp, &result);
     *ip = (@type@) result;
     return ret;
}


If I'm reading this right, this gets called for the datatype of 
interest, and it is passed in a pointer to the file that is being read.

if I have NumPyOS_ascii_ftolf right, it should return 0 if it doesn't 
succesfully read a number. However, this looks like it sets the data in 
*ip, even if the return value is zero.

It does pass on that return value, but, from ctors.c:

fromfile_next_element(FILE **fp, void *dptr, PyArray_Descr *dtype,
                       void *NPY_UNUSED(stream_data))
{
     /* the NULL argument is for backwards-compatibility */
     return dtype->f->scanfunc(*fp, dptr, NULL, dtype);
}

just moves it on through. This is called from here:

         if (next(&stream, dptr, dtype, stream_data) < 0) {
             break;
         }

which is checking for < 0 , so if a zero is returned, it will just go in 
its merry way...

So, have I got that right?

Should this get fixed at that last point?

One more point, this is a bit different for fromfile and fromstring, so 
I'm getting really confused!

-Chris









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Christopher Barker, Ph.D.
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