Why the output is "the sum is 55"?

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1.00/5 (1 vote)

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Python

<pre># Program to illustrate a loop with condition at the top

# Try different numbers
n = 10

# Uncomment to get user input
#n = int(input("Enter n: "))

# initialize sum and counter
sum = 0 
i = 1 

while i <= n:
   sum = sum + i
   i = i+1    # update counter

# print the sum
print("The sum is",sum)

What I have tried:

I did not understand this,it is not clicking with me.

Posted 30-Apr-18 3:57am

Member 13798091

Updated 30-Apr-18 7:27am

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Rajesh Anuhya 30-Apr-18 10:09am

What do you think? Result should be 555 ????..

Rajesh Anuhya 30-Apr-18 10:09am

It's Correct only ..

Richard Deeming 30-Apr-18 10:43am

Simple maths: the sum of the integers from 1 to n is n × (n + 1) ÷ 2

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Patrice T · Accepted Answer · 2018-04-30T07:28:00

Quote:
Why the output is "the sum is 55"?

Want to watch this code building the answer by yourself ?

Run your code on debugger step by step, and inspect variables.

The debugger is here to show you what your code is doing .
There is no magic in the debugger, it don't know what your is supposed to do, it don't find bugs.

To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.
Debugger - Wikipedia, the free encyclopedia[^]
27.3. pdb — The Python Debugger — Python 3.6.1 documentation[^]
Debugging in Python | Python Conquers The Universe[^]
pdb – Interactive Debugger - Python Module of the Week[^]
The debugger is here to only show you what your code is doing and your task is to compare with what it should do.

OriginalGriff · Accepted Answer · 2018-04-30T04:17:00

Solution 1

Because that is what you told it to do!
Look at the values at the end each time you go round the loop:

 i Sum
 2   1
 3   3
 4   6
 5  10
 6  15
 7  21
 8  28
 9  36
10  45
11  55
The sum is 55

Posted 30-Apr-18 4:17am

OriginalGriff

Comments

Member 13798091 30-Apr-18 10:20am

yeah, i got it thank you very much.
that was what i really needed.

OriginalGriff 30-Apr-18 10:27am

You're welcome!