[SciPy-dev] Fancy indexing curiosity

Travis Oliphant oliphant.travis at ieee.org
Sun Jan 8 01:09:28 CST 2006


Sasha wrote:

>>>>x = array([1])
>>>>m = array([1], bool)
>>>>x[m] = ''
>>>>x
>>>>        
>>>>
>array([12998744])
>  
>
>>>>x[m] = ''
>>>>x
>>>>        
>>>>
>array([12998752])
>
>It looks like x gets the address of the '' object (note the number change).
>This "feature" is present in 0.9.2 release and in svn 0.9.3.1831
>  
>

Thanks for this corner case.  Actually, it's getting whatever is in the 
memory allocated.

Try

b = array('',x.dtype)

b should be a size-0 array,  (there is actually 1 elementsize of memory 
allocated for it though).

The mapping code is iterating over b and resetting b whenever it runs 
out of elements of b (every time in this case), except the data pointed 
to by the iterator is never valid so this should not be allowed....

I suppose instead, creating an iterator from a size-0 array could raise 
an error.  This would be a great and simple place to catch this in the 
code as well.

A size-0 array has nothing to iterate over...


-Travis






More information about the Scipy-dev mailing list