[Tutor] please help - stuck for hours

[ADRIAN KELLY]

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?? 

  # -*- coding: cp1252 -*-def exchange(cash_in):    euro=1    dollar=1.35    base=50    if cash_in>base:        totalreturn=cash_in*dollar    else:        totalreturn=0    return totalreturn

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      main()

Adrian Kelly 
1 Bramble Close

Baylough

Athlone

County Westmeath

0879495663


From: waynejwerner at gmail.com
Date: Thu, 17 Nov 2011 15:35:29 -0600
Subject: Re: [Tutor] please help - stuck for hours
To: kellyadrian at hotmail.com
CC: tutor at python.org

On Thu, Nov 17, 2011 at 3:19 PM, ADRIAN KELLY <kellyadrian at hotmail.com> wrote:







i have tried everything, i am trying to build in a loop to my 2 functions which worked fine up until my latest sorti.
please have a look if you can..............



def exchange(cash_in):    euro=1    dollar=1.35

    base=50    if cash_in>base:        totalreturn=cash_in*dollar

    else:        totalreturn=0    return totalreturn



def main():

    amount=""    while amount<50:        print 'Sorry, cannot convert an amount under €50 '

        amount = input('how much do you want to change:')    else:

        total=exchange(amount)        print 'Your exchange comes to: ',total

      main()


 
Traceback (most recent call last):

  File "F:\VTOS ATHLONE\PYTHON_VTOS\foreign exchange\f_ex3.py", line 27, in <module>    main()  File "F:\VTOS ATHLONE\PYTHON_VTOS\foreign exchange\f_ex3.py", line 19, in main

    total=exchange(amount)  File "F:\VTOS ATHLONE\PYTHON_VTOS\foreign exchange\f_ex3.py", line 7, in exchange    totalreturn=cash_in*dollar

TypeError: can't multiply sequence by non-int of type 'float'
Thank you for posting the full traceback - this last line tells you the exact problem - you're trying to multiply a sequence by a float (in this case your sequence is a string). The line right above that tells you the what you tried to do: multiply `cash_in` by `dollar`.


Take a look at your code and what do you see? Well, you set `dollar = 1.35`, and you don't change the value elsewhere so that's certainly a float. What about cash_in? Well if you work your way backwards through the traceback you see that it was called with the parameter "amount".


Where is amount set? Ah, on that line:
amount = input()
This line is extremely problematic. First, I see by your print statement that you're using  Python 2.x, so input is actually executing arbitrary code. What you *want* is raw_input which returns a string and is much MUCH safer.


I don't know what your input value was, but I suspect that you did something like '30' (with the quotes), because otherwise it would evaluate to an integer. It's also possible that you used `amount`, which would evaluate to "" since you already declared it. None of these things are good.


Change your initial assignment to :
    amount = 0
and the input line to:
    amount = float(raw_input("How much would you like to exchange? "))


This will first get a string from the user and then convert it to a float - which I suspect you'll want, since you're dealing with monetary values.HTH,Wayne 		 	   		  
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