CODEWITHSUNDEEP
python-3.6
Ketan Tiwari
Ketan Tiwari

Reputation: 31

What is wrong with this Python code for finding an Armstrong number?

I'm trying to write a Python program that will return an Armstrong number and the resulting outputs do not meet my expectations. An Armstrong number in a given number base is a number that is the sum of its own digits each raised to the power of the number of digits.

for i in range(0,len(lst)):
    lst[i] = int(lst[i])
sum2= 0

for i in range(0,len(lst)):
    sum1 = lst[i]*lst[i]*lst[i]
    sum2 += sum1
if sum2 == n :
    print("Armstrong number")
else:
    print("Not an Armstrong number")

Why is this code returning incorrect results?

Upvotes: 0

Views: 176

Answers (2)

VivekP
VivekP

Reputation: 11

You need to cast n as answered above!

Also Armstrong number is not just power of 3

The power is equal to number of digits present in the number.

For Eg :

153 has 3 digits 1 5 and 3 so 1^3 + 5^3 + 3^3 = 153

But if number is 4 digit Number then :

Input : 1634

Output : 1634 is an Armstrong Number

1^4 + 6^4 + 3^4 + 4^4 = 1634

and so on!

So basically the power is no. of digits present in the given no.

Here is my simple piece of code for it :

def Armstrong(num):
    exp = len(num)
    res = 0
    for i in num:
        res += pow(int(i),exp)
    if res == int(num):
        print(num + " is an Armstrong Number")
    else:
        print(num + " is not an Armstrong Number")
num=input("Enter a number : ")
Armstrong(num)

Upvotes: 1

rhurwitz
rhurwitz

Reputation: 2747

You are very, very close. The only problem is that n is a string, not an int, so when you compare it to sum2 it will never be equivalent. Cast n to an int and problem solved:

if sum2 == int(n):

If you want to see a more streamlined way to get the same result, here is an example:

value_string = input("Enter an integer value: ")

starting_value = int(value_string)
digits = [int(char) for char in value_string]

cubed_sum = sum([
    one_digit ** 3
    for one_digit in digits
])

if cubed_sum == starting_value:
    print(f"{starting_value} is an Armstrong number.")
else:
    print(f"{starting_value} is not an Armstrong number.")

Upvotes: 0

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