If the number is negative, it is not a prime by definition. Using the absolute value would result in incorrect responses.

That's right, comment edited.
Thanks.

It hasn't been removed, just moved to functools.

There you go!
https://docs.python.org/2/library/functions.html#reduce

I need help with the second function. I am not able to clearly understand the usage of alphabets, could anyone explain it in a little more detail? Does it mean that we need to assign certain numerical values to these alphabets as well?
Thank you!!

what is reduce, what does it do?

speechless it is amazing. masterpiece..

the question also prompted for negative inputs. Of course mathematically we define for positive integers.

just add a line of code
num = abs(num)