Sorting through data

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This is similar to an example from a book I'm learning to code from. I have a single function that I would like to have the input data sorted according to the parameters of the "for" construction at the bottom, but the "for" construction doesn't sort out the data input into the "sales" list. What am I doing wrong? I'm learning so be gentle! :)

Python

def sort_high_to_low(user_prompt="Please enter the amount of stands you want to enter sales for: "):
    user_input = int(input(user_prompt))
    sales = []
    for count in range(1, user_input + 1):
        prompt = "Please enter the sales for stand " + str(count) + ": "
        sales.append(int(input(prompt)))


    print(sales)


    for sort_pass in range(0, len(sales)):
        for count1 in range(0, len(sales)-1):
            if sales[count1] < sales[count1 + 1]:
                temp = sales[count1]
                sales[count1] = sales[count1+1]
                sales[count1+1] = temp

sort_high_to_low()

What I have tried:

I have tried returning the sales just before the second "for" construction.

I have used sales.sort(), it does work but I want to see how the sorting function at the bottom will work with input data.

Posted 10-Nov-19 5:15am

totalartist

Updated 10-Nov-19 8:22am

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Richard MacCutchan 10-Nov-19 12:29pm

How can you tell it does not work since you do not print the sorted list?

[edit]
I just tried it and it sorts into descending order.
[/edit]

totalartist 10-Nov-19 12:38pm

Are you telling me a simple "print" statement was all I had to add to display the sorted list?

totalartist 10-Nov-19 12:39pm

I just added a "print" statement and like you said, it worked. Thank you very much for your input, I do appreciate it.

Richard MacCutchan 10-Nov-19 12:56pm

You're welcome.

Patrice T 10-Nov-19 14:33pm

If problem solved, accept a solution to close the question.
You can also publish your own solution.

2 solutions

Solution 2

Quote:
but the "for" construction doesn't sort out the data input into the "sales" list.

Your code do not behave the way you expect, or you don't understand why !

There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
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[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

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.

Posted 10-Nov-19 8:22am

Patrice T

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OriginalGriff · Accepted Answer · 2019-11-10T06:05:00

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#

def Double(value)
   return value * value

Once you have an idea what might be going wrong, start using the debugger to find out why: pdb — The Python Debugger — Python 3.8.0 documentation[^]
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!