[Numpy-discussion] Zero Division not handled correctly?

Skipper Seabold jsseabold@gmail....
Sun Dec 6 15:16:08 CST 2009


I believe this is known, but I am surprised that division by "integer"
zero results in the following.

In [1]: import numpy as np

In [2]: np.__version__
Out[2]: '1.4.0.dev7539'

In [3]: 0**-1 # or 0**-1/-1
---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)

/home/skipper/school/Data/ascii/numpy/<ipython console> in <module>()

ZeroDivisionError: 0.0 cannot be raised to a negative power

In [4]: np.array([0.])**-1
Out[4]: array([ Inf])

In [5]: np.array([0.])**-1/-1
Out[5]: array([-Inf])

In [6]: np.array([0])**-1.
Out[6]: array([ Inf])

In [7]: np.array([0])**-1./-1
Out[7]: array([-Inf])

In [8]: np.array([0])**-1
Out[8]: array([-9223372036854775808])

In [9]: np.array([0])**-1/-1
Floating point exception

This last command crashes the interpreter.

There have been some threads about similar issues over the years, but
I'm wondering if this is still intended/known or if this should raise
an exception or return inf or -inf.  I expected a -inf, though maybe
this is incorrect on my part.

Skipper


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