[Tutor] dealing with user input whose value I don't know

[David]

Oh, great, this answers my question!

Thanks!

David


christopher.henk at allisontransmission.com wrote:
>
> I am not sure how you got from the input to your variable i, it is a 
> good idea to post your code as well.
>
> That said raw_input will return the user's input as a string which you 
> then need to convert to integers.
> So the commas are brought in as well.
> You can solve this in a couple of ways:
> First, you can split the string on the commas and get a list of 
> strings each representing one of the numbers.
>
>         numberlist=numbers.splt(",")
> will give you:
>         numberslist=["1","2"]
> which you can then loop over and convert to integers and add up.
>
> Secondly, you can have the users input the numbers one at a time 
> inside the loop.
> add = add + int(raw_input("Please type the next number:"))
>
> Chris
>
>
>
>
> *David <ldl08 at gmx.net>*
> Sent by: 
> tutor-bounces+christopher.henk=allisontransmission.com at python.org
>
> 10/02/2008 02:06 PM
>
> 	
> To
> 	tutor at python.org, 
> tutor-bounces+christopher.henk=allisontransmission.com at python.org
> cc
> 	
> Subject
> 	Re: [Tutor] dealing with user input whose value I don't know
>
>
>
> 	
>
>
>
>
>
> Cheers for the insights!
>
> However, I just found out that changing input() to raw_input() breaks my
> code:
>
> This program takes the average of numbers you supply!!
> How many numbers do you want me to work with? 2
> You want me to take the average of 2 numbers.
> Please type the numbers, separated by commas: 1,2
> You want to know the average of the numbers: 1,2
> Traceback (most recent call last):
>  File "avgInput.py", line 13, in <module>
>    add = add + i
> TypeError: unsupported operand type(s) for +: 'int' and 'str'
>
> **** End of process output ****
>
> The reason being, I take, that
>
> numbers = raw_input("Please type the numbers, separated by commas: ")
>
> also returns the comma (1,2) and thus the for loop can't cope...
> So should I therefore retain
>
> numbers = input("Please type the numbers, separated by commas: ") ?
>
> Otherwise I don't know (yet) what to do....
>
> David
>
>
> Bill Campbell wrote:
> > On Thu, Oct 02, 2008, Steve Willoughby wrote:
> >  
> >> On Fri, Oct 03, 2008 at 01:38:48AM +0800, David wrote:
> >>    
> >>> Does that mean input() is obsolete (after all, Zelle's book is not 
> the
> >>> freshest on the shelf)? Or do they have different uses?
> >>>      
> >> Depends on how you look at it.
> >>
> >> input() automatically evaluates whatever the user types as a Python
> >> expression and returns the result.  So if they type 5, the integer
> >> 5 is returned.  For your program, that's probably what you want, and
> >> has the advantage of letting you type something like 2+3 so your user
> >> can let Python evaluate math expressions.
> >>
> >> On the other hand, you'd think that you could ask a user for a text
> >> response using input():
> >>   name = input("What is your name? ")
> >>   print "Hello, ", name
> >>
> >> But if they just type the answer, Python will crash with an error
> >> because it's expecting a legal Python expression there (so a
> >> string value would have to be typed in quotes).
> >>    
> >
> > Remember the cardinal rule NEVER TRUST USER INPUT!  Always check
> > for validity, and use methods that prevent malicious strings from
> > allowing the user to get unauthorized access or change things
> > they shouldn't.
> >
> > Many of the common exploits of web pages are the result of poor
> > checking of input resulting in sql injection attacks, and other
> > breaches.
> >
> > Bill
> >  
>
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