[Numpy-discussion] abs for max negative integers - desired behavior?

Matthew Brett matthew.brett@gmail....
Tue Oct 11 13:23:15 CDT 2011


Hi,

I recently ran into this:

In [68]: arr = np.array(-128, np.int8)

In [69]: arr
Out[69]: array(-128, dtype=int8)

In [70]: np.abs(arr)
Out[70]: -128

Of course, I can see why this happens, but it is still surprising, and
it seems to me that it would be a confusing source of bugs, because of
course it only happens for the maximum negative integer.

One particular confusing result was:

In [71]: np.allclose(arr, arr)
Out[71]: False

I wanted to ask whether this is the desired behavior, and whether it
might be worth planning a change in the long term?

Best,

Matthew


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