I can´t understand why this Python code is wrong

Question

1.00/5 (1 vote)

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The code is meant to allow the user to write numbers until the user insert a -1, then every single digit the user has typed has to contribute to the total sum of all digits.

I´ve tried something but my compiler gives me an error:
File "<string>", line 14, in <module>
ValueError: invalid literal for int() with base 10: '-'

Sorry for bad english if that´s the case

Also my code is indented but I cannot make the indentions here, don´t know how to

What I have tried:

Python

print("Introduce números enteros")
n=0
SUMA=0
suma=0
while n!=-1:
    n=int(input("==> "))
    while n<-1:
        print("Solo valen números iguales o mayores que -1")
        n=int(input("==>"))
    c=(len(str(n)))-1
    suma=0
    while c>=0:
        x=(str(n)[c])
        x=int(x)
        suma=suma+x
        c=c-1
    SUMA=SUMA+suma
print(SUMA)

Posted 7-Oct-22 15:12pm

Artatacjahalolctm Jaja

Updated 7-Oct-22 21:44pm

Patrice T

v3

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OriginalGriff 8-Oct-22 0:23am

To keep the indentation, you can select "code block" from the popup when you paste it in, use the "code" widget above the textbox, or manually insert "pre" tags. You will end up with the result Patrice has done for you.
Use the "Improve question" widget and look at what surrounds your code to see what the end result looks like and it'll be pretty simple for you next time.

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OriginalGriff · Answer 1 · 2022-10-07T18:29:00

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

C#

int Double(int value)
   {
   return value * value;
   }

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.

This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

Richard MacCutchan · Answer 2 · 2022-10-07T21:44:00

Solution 2

You are not checking if the input value is -1:

Python

while n!=-1:
    n=int(input("==> ")) # you need to add the following after this line
    if n == -1:
        break

Posted 7-Oct-22 21:44pm

Richard MacCutchan