CODEWITHSUNDEEP
pythoninfinite-loop
Psyduck
Psyduck

Reputation: 667

Infinite loop debug

I wrote a function to tell if certain number is a perfect number: a number is a perfect number if the summation of all it's factor equals to itself.

The function goes like:

def is_perfect(n):
    l = [1]
    temp = n
    while temp != 1:
        for i in range(2,n):
            if temp % i ==0:
                l.append(i)
                temp = int(temp / i)
                break
    if sum(l)==n:
        return True
    else:
        return False

I want it to return boolean value according to the input. Then I want to use a for loop to find out all the perfect number with my function above, but it seems there's a infinite loop. Where am I wrong?

a=[]
for x in range(1,1001):
        if is_perfect(x):
            a.append(x)

print([x for x in a])

Upvotes: 0

Views: 569

Answers (1)

MatTheWhale
MatTheWhale

Reputation: 977

Your function goes into an infinite loop when a prime number is passed in. This is because your while loop condition depends on temp being modified upon every iteration, but if n is prime this never happens. The reason why is in this line:

if temp % i == 0:

When n is prime the code in your if-statement block gets passed over completely, including the line that reassigns the temp variable.

Upvotes: 1

Related Questions