[Tutor] Help on IF Statements

Daniel Yoo dyoo@hkn.EECS.Berkeley.EDU
Mon, 31 Jul 2000 23:29:02 -0700 (PDT)


Dear Emo,

Hello!  Ok, let's take a look.


On Mon, 31 Jul 2000, emo sofia wrote:

> 1.  to type it: but the result is err
> 	>>> x = int(raw_input("Please enter a number: "))
> Please enter a number: 
> Traceback (innermost last):
>   File "<pyshell#2>", line 1, in ?
>     x = int(raw_input("Please enter a number: "))
> ValueError: invalid literal for int():


Hmm... this appears to work for me:

###
>>> x = int(raw_input("Please enter a number: "))
Please enter a number: 23
>>> x
23
###

However, if I press enter at the prompt instead, it'll trigger the same
error message:

###
>>> x = int(raw_input("Please enter a number: "))
Please enter a number: 
Traceback (innermost last):
  File "<stdin>", line 1, in ?
ValueError: invalid literal for int(): 
###

I'm not quite sure if that's what's happening with your program.  You
might want to temporarely hard-code values of 'x' into your program, since
you're learning about if-statements.  Your programs seem fine --- it might
just be strangeness with input/output.

If you're familiar with your text editor and command prompt, you might
want to write your program into a '.py' file, and try using programs with
raw_input() there.  Doing this might make things easier --- you can
correct typos without rewriting the whole section of code.