Python Course - while loops

Question

Hi Guys !

I'm actually on the Python course and I'm looking for the solution of a pro problem in the while loops section.

The problem ask to calculate the sum of all the digits of an integer input. And my solution for me was that :

n = int(input())
sum = 0
length = 0

while n > 0:
n //= 10
length += 1
sum += length

print(sum)

For me, the variable n is for the input of the users.
Lenght is for calculate the number of digits.
I understand that. So I create a variable sum for calculate the sum of all the lenght who are generate by the while loop.

With that, I would have the result that the problem want. But it's not the case and I don't know why.

Someone can explain me my error ?

Thanks !

Answer 1

Okay ! My error was to consider the lenght like the digit in my head but I see with your example that it two things totally different !

Thanks for your help guys !

Answer 2

The sum of all lengths differs from the sum of all digita , what you should've wrote instead is
while n>0:
sum+=n%10
length+=1
n//=0
% is the mod operation which will give you the last digit when you use it with 10

you can test it here
https://code.sololearn.com/cySw7yFuI5bD/?ref=app

Answer 3

Greg GS
You could also use a list comprehension to split and add them.

number = int(input())
add = sum( [int(x) for x in str(number)] )
print(add)

What I have done is convert the number to a sting, loop over each element and turn them back to an integer then used the sum function.

Also, try not to use "sum" as a variable name.

Happy Coding 😀

Answer 4

Wow great example too Tomiwa Joseph !
But why not to use sum as a variable name ?

Answer 5

Greg GS
You can use it as long as you won't use the sum function in your code.
Example:
sum = 4
print(sum([1,2,3]))

You get an error because you have overwritten the sum function with 4.
Python won't understand print(4([1,2,3]))... I don't understand it either 😃

Answer 6

And I don't understand it too. I get it. Thanks for your help !