Why Is My Code Displaying The Wrong Output?

I wrote a code that outputs 'Yes' when the input number is a perfect number, and outputs 'No' when the number isn't. But when I input 6, it outputs 'No'. I have specified it to pri

Solution 1:

Sorry for the confusion regarding my previous answer. The problem was that you were appending n instead of i in myList.append(n). Moreover, you could simply use sum to sum your list.

Your output was wrong because you were appending the number n and hence when you do sum=sum+myList[i], you were just adding n to the sum three times because instead of adding 1, 2, 3 to sum, you were adding 6, 6, 6.

n=int(input())
myList=[]

for i inrange(1,n):
    if n%i==0:
        myList.append(i)

ifsum(myList)==n:
    print("Yes")
else:
    print("No")

A one liner suggested by Matthias

print(('No', 'Yes')[sum(i for i inrange(1, n) ifnot n % i) == n])

Solution 2:

There is a cool one liner in comment section of this answer

other have already pointed out your mistake so here is how you can optimize your code a little bit.

greatest divisor of 6( =n) other than 6 is 3( = n//2) since we don't add number itself to factors_sum while checking whether sum of factors equals to number( ie while finding perfect number),so we don't need to check whether any number greater than 3 is a factor of 6 or not.

# perfect nums example 6, 28, 496, and 8,128
n = 8128
stop = (n//2) +1# stop is exclusive thats why extra 1    
factors_sum = 0for i inrange(1,stop):
    if n % i == 0:
        factors_sum += i

print('Yes'if factors_sum == n else'No') # Yes'''
benchmark result( using timeit ran each five times)
for smaller value of n there is no significant difference but as the value of n becomes very large you can clear see the difference.
n = 33550336
1)    stop = (n//2) +1
      6.580396663 ( time in secs)

2)    stop = n
      12.635774489000001 ( time in secs)
'''