[Tutor] please help - stuck for hours

Wayne Werner waynejwerner at gmail.com
Thu Nov 17 23:53:59 CET 2011

On Thu, Nov 17, 2011 at 4:32 PM, ADRIAN KELLY <kellyadrian at hotmail.com>wrote:

> thanks very much, great response really really appreciated it and now i
> understand. i hate to ask again but can you see why it won't print the
>  'enter and amount over 50' in the right place??

Computers are unfailingly stupid machines. They will do whatever wrong
thing you tell them to do every single time.

>  <snip>
> def main():
>     amount=0
>     while amount<50:
>         amount = input('how much do you want to change:')
>         print 'enter an amount over €50: '
>     else:
>         total=exchange(amount)
>         print 'Your exchange comes to: ',total

Sometimes it helps writing out the logic in steps before you translate it
to code. In this case my guess is that these are the steps you want:

  1. Get a value from the user (you're still using input - stop that, it's
dangerous! input is   only a good function in 3.x where it replaces

  2. If the value is less than 50, tell the user to enter an amount > 50
and repeat step 1

  3. Otherwise, exchange the amount and display that.

Right now, these are the steps that you're doing:

  1. Get a value from the user

  2. Display the error message

  3. If the value is < 50, go to 1

  4. exchange the amount

  5. display the amount.

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