math.pow vs pow

[Peter Otten]

Georgy Pruss wrote:

> 
> "John J. Lee" <jjl at pobox.com> wrote in message
> news:87k75lmlru.fsf at pobox.com...
> | For some applications, getting a complex result means you've made a
> | mistake.  And some people don't know what a complex number is, and
> | would rather have their teeth drilled than find out.
> 
> Can you provide an example when pow with real arguments gives a complex
> result, please?

He could, if Python were not so reluctant:

>>> pow(-5,.5)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
ValueError: negative number cannot be raised to a fractional power

Sad day for the dentist:-)
But:

>>> pow(complex(-5), .5)
(1.3691515264124976e-16+2.2360679774997898j)

>>> pow(-5, complex(.5))
(1.3691515264124976e-16+2.2360679774997898j)

as you might expect.

Peter