Logic issue - sum of numbers

Question

I need some help with the logic of a program. What I am trying to do:

Write a program with a loop that asks the user to enter a series of positive numbers. The user should enter a negative number to signal the end of the series. After all the positive numbers have been entered, the program should display the sum.

keep_going = ' '
max = ()
total = 0.0

print('This program will add numbers together until a negative number is entered.')
print('It will then show the total of the numbers entered.')

while keep_going != (-):
    number = int(input('Enter a number: '))
    total = total + number

print('The total is', total)

Where am I going wrong?

This `(-)` doesn't look like valid syntax. – Hunter McMillen Jun 13 '14 at 15:21 — Hunter McMillen, Jun 13 '14 at 15:21

score 5 · Accepted Answer · answered Jun 13 '14 at 15:20

5

Use an infinite loop and test if the number just entered is smaller than 0:

total = 0

while True:
    number = int(input('Enter a number: '))
    if number < 0:
        break
    total = total + number

Only by testing the number just entered can you detect when a negative number has been entered.

answered Jun 13 '14 at 15:20

Martijn Pieters

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Should you check the return value of `input()` before applying `int()`? – Hunter McMillen Jun 13 '14 at 15:22
@HunterMcMillen: You can use exception handling, but by the looks of it this is a beginner, learning to program. Tutorials often assume the user will just enter valid numbers and introduce exception handling later. – Martijn Pieters Jun 13 '14 at 15:24
Yeah, but just to be clear the program will crash if I enter `'a'` – Hunter McMillen Jun 13 '14 at 15:25
1

@HunterMcMillen: see [Asking the user for input until they give a valid response](http://stackoverflow.com/a/23294659) for best practices. – Martijn Pieters Jun 13 '14 at 15:26
Thank you very much! I am having a day.... – user3030048 Jun 13 '14 at 19:34

score 0 · Answer 2 · answered Jun 13 '14 at 15:20

0

You never change the value of keep_going, so your loop will never terminate.

answered Jun 13 '14 at 15:20

Andrew

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You cannot even test against `(-)`; that's an operator in parentheses, and not legal syntax. – Martijn Pieters Jun 13 '14 at 15:21
I figured that was the case too, but I don't know much Python. – Andrew Jun 13 '14 at 15:22

Logic issue - sum of numbers

2 Answers2