我的 Python 代码出现数学域错误，不知道该怎么做

Question

I'm trying to do some code for the Josephus Problem, but I keep getting a weird error. My code looks like this:

import math
power = 2
originalnumber = int(input("how many to start?"))
powerof2 = math.log(originalnumber,power)
if type(powerof2) == int:
    powerof2tf = True
    winningseat = 1
else:
    powerof2tf = False
    newnumber = originalnumber
    while True:
        newnumber = newnumber - 1
        variabletest = type(math.log(newnumber,power))
        if variabletest == int:
            break
        else:
            pass
    winningseat = 1+2*(originalnumber-newnumber)

print("the winning seat is", winningseat)

When I try to run it it gives me this error:

ValueError Traceback (most recent call last)

in ()

 12         import math

 13         newnumber = newnumber - 1

---> 14 variabletest = type(math.log(newnumber,power))

 15         if variabletest == int:

 16             break

ValueError: math domain error

Any ideas? I have no clue how to fix this.

Answer 1

You are getting the error because math.log(0, 2) is undefined . Here's a good site to refresh your knowledge on how log works in general math.

log 0 is undefined. It's not a real number, because you can never get zero by raising anything to the power of anything else. You can never reach zero, you can only approach it using an infinitely large and negative power.

You need to revise your code to handle newnumber getting to zero, then this problem will go away.