Summation with for loop in python

Question

I input 10 to the below sequence, the it prints sum = 56 I list what sum includes, they are 1,2,3,4,5,6,7,8,9,10. I wonder what's wrong with the calculation of sum.

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n = int(input('input number?'))

sum = 1


for i in range(1,n+1,1):

     sum += i


print(sum)

You are starting the loop from one and also have initialized the sum with 1. It is a logical error rather than a programmatical one. Try setting up sum = 0. Note: default steps are 1 in Python loop, so the third param in the range is unnecessary. — Jonti
– Jonti, Commented Mar 24, 2021 at 7:03
Also, sum is a builtin, change it to something like 'sumval' instead. For instance: "sum([1,2,3,4,5,6,7,8,9,10])" should give you "55". — learning2learn
– learning2learn, Commented Mar 24, 2021 at 7:06

Daisuke Akagawa · Accepted Answer · 2021-03-24 07:03:26Z

1

That's because you first define sum = 1. The true result is 55 but you increment it by yourself.

true code is below

n = int(input('input number?'))
result = sum(range(1, n+1))

You should not use sum as a variable name because sum is a built-in function. And in this case, you can calculate summantion by sum so easily.

answered Mar 24, 2021 at 7:03

Daisuke Akagawa

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Grigori Demin · Accepted Answer · 2021-03-24 07:15:46Z

0

I don't know why the variable 'sum' is initialized to 1. It should be 0. You will get the correct result. :)

answered Mar 24, 2021 at 7:15

Grigori Demin

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