[Tutor] FW: null inputs

[James Reynolds]

On Thu, Mar 15, 2012 at 10:32 AM, ADRIAN KELLY <kellyadrian at hotmail.com>wrote:

>
>
> Adrian Kelly
> 1 Bramble Close
> Baylough
> Athlone
> County Westmeath
>
> 0879495663
>
>
>  ------------------------------
> From: kellyadrian at hotmail.com
> To: tutor at python.org
> Subject: null inputs
> Date: Thu, 15 Mar 2012 14:19:16 +0000
>
> Hi guys,
> how do i prevent a user from leaving a blank when inputting?
>
> e.g.
> age=int(input("what age are you? ")).................. i want to stop the
> user pressing enter!!!!
>
> if age==""?????
>
>
>   ************************************
> age=raw_input("what age are you? ")
> if age=="":
>     age=int(age)
>     print "please enter your age"
> else:
>     print "your age is ",age
>  *************************************
> i have tried this but still no luck, if anyone can help i would
> apprecitate it
>
>
>
> Adrian Kelly
> 1 Bramble Close
> Baylough
> Athlone
> County Westmeath
>
> 0879495663
>
>
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You can't prevent users from entering whatever they feel like it, but you
can prevent your program from processing that input and force them to try
again.

The typical way this is done is through a while loop:

age = ''

while age != ''
    age=raw_input("what age are you? ")

this will continue to loop until you give it something other than ''.

Of course, you can build on this, you know, something like:

checker = False

while checker:
    age=raw_input("what age are you? ")
    try:
        age = int(age)
        checker = True
    except TypeError:
      print "you didn't enter an integer for an age!"
      print "try again!!!
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