[Tutor] Python program malfunction

[Peter Otten]

Jag Sherrington wrote:

> Hi,
> There appears to be a problem with this program.
> It is taken from the "Starting out with Python" book third edition.
> 
> The problem is when the "validate the wholesale cost" is introduced.
> Without the validator the code works fine, but with it the code won't let
> you enter a positive wholesale cost unless you do a negative cost first.
> Even after you have entered a negative cost and got the results of your
> positive cost it asks wether you want to do another item if you type "y"
> you still can't enter a positive amount.
> 
> HERE IS THE CODE AS COPIED FROM THE BOOK:
> 
> #This program calculates retail prices.
> 
> mark_up = 2.5  # The mark up percentage.
> another = 'y'   # Variable to control the loop.
> 
> # Process one or more items.
> while another == 'y' or another == 'y':
>     #Get the item 's wholesale cost'
>     wholesale = float(input("Enter the item's wholesale cost: "))
> 
>     # Validate the wholesale cost.
>     while wholesale < 0:
>         print('ERROR: the cost cannot be negative.')
>         wholesale = float(input('Enter the correct wholesale cost: '))

Look at the indentation of the rest of your code. To which while loop do you 
want it to belong and in which while loop is it actually executed?
 
>         #Calculate the retail price.
>         retail = wholesale * mark_up
> 
>         #Display the retail price.
>         print('Retail price: $', format(retail, ',.2f'), sep='')
> 
>         #Do this again.
>         another = input('Do you have another item? ' + \
>                         '(Enter y for yes): ')
> 
> HERE ARE THE RESULTS:
> 
> Enter the item's wholesale cost: 0.50
> Enter the item's wholesale cost:    (THIS SEEMS TO BE A PROBLEM)
>>>> ================================ RESTART
>>>> ================================
>>>> 
> Enter the item's wholesale cost: -0.50  (YOU HAVE TO ENTER A NEGATIVE
> FIRST ???) ERROR: the cost cannot be negative.
> Enter the correct wholesale cost: 0.50
> Retail price: $1.25
> Do you have another item? (Enter y for yes): y
> Enter the item's wholesale cost: 0.50
> Enter the item's wholesale cost:
> 
>  
> THANK YOU FOR YOUR HELP.
> 
> Regards, Jag