Keep getting a "Traceback" error when running simple program

Question

I am new to this and I really don't understand why this is happen. I am trying to run this program:

            NumberToCheck=0
            check=2

            def checker():
                global NumberToCheck
                global check
                check=2
                while check < NumberToCheck:
                    if NumberToCheck % check == 0:
                        main()
                    check=check+1
                else:
                    divider()

            def main():
                global NumberToCheck
                while NumberToCheck < 600:
                    NumberToCheck=NumberToCheck+1
                    checker()

            def divider():
                if 600851475143 % NumberToCheck == 0:
                    print (NumberToCheck)
                    end()
                main()

            def end():
                print ("end")

            print ("start")
            main()

And I keep getting this error:

            start
            1
            71
            Traceback (most recent call last):
              File "/Users/marknorman/Documents/Problem 3.py", line 29, in <module>
main()
              File "/Users/marknorman/Documents/Problem 3.py", line 21, in main
checker()
              File "/Users/marknorman/Documents/Problem 3.py", line 15, in checker
divider()
              File "/Users/marknorman/Documents/Problem 3.py", line 26, in divider
main()

And this would go forever in what looks like a random order unless I stop it.

Help?

That's not the full error. We need to see the whole thing. Also, you should read [mcve]. We need to see the exact code you're running. In Python, indentation is super important, so it'll be worth your time to get that fixed. — Morgan Thrapp, May 12 '16 at 19:07
It is infinite. I have left it running for several minutes and it keeps printing that out. — Mark Norman, May 12 '16 at 19:08
It looks like the error is `Maximm recursion depth exceeded ` — zondo, May 12 '16 at 19:11

Keatinge · Answer 1 · 2016-05-12T19:18:08.490

2

Remove the main() in divider. You're getting infinite recursion because instead of returning to main naturally you are calling the main() method again which starts the process over again.

Also as a side note I would really suggest you stop using all these global variables. Return values from your functions instead

Here's a much simpler version that still uses a function. (For a problem like this you really don't even need functions anyway but it looks like you're trying to practice them)

def main():
    numberToCheck = 600851475143
    i = 2

    #infinite loop
    while 1:
        if isDivisibleBy(numberToCheck, i):
            # if our number is divisible print it out and stop the loop
            print(numberToCheck, "is divisible by", i)
            break
        i += 1 #increment i

def isDivisibleBy(dividend, divisor):
    if dividend % divisor == 0:
        return True
    return False


if __name__ == "__main__":
    main()

Also note that the function isDivisibleBy could be shorted to just:

def isDivisibleBy(dividend, divisor):
    return dividend % divisor == 0

But I figured that would be a little confusing for a beginner.

edited May 12 '16 at 19:18

answered May 12 '16 at 19:09

Keatinge

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Thanks! That's it. – Mark Norman May 12 '16 at 19:11
I'll post an update with how you should refactor this code to not use global variables in a few minutes too – Keatinge May 12 '16 at 19:11
Looking forward to it! What is the problem with global variables? – Mark Norman May 12 '16 at 19:16
I've updated my post. Instead of having global values that get referenced by the functions you should instead pass around values using return statements. There's a massive list of reasons why you shouldn't use global variables in a situation like this, mainly because they are indicative of poor design. Here's a much better explanation than I could ever give: http://stackoverflow.com/questions/19158339/why-are-global-variables-evil – Keatinge May 12 '16 at 19:20

Keep getting a "Traceback" error when running simple program

1 Answers1