[Tutor] Hello and a (probably) stupid question

[Reggie Dugard]

Chris,

Hi, glad to hear you're interested in Python!  Your problem illustrates
the importance of indentation in Python.  In your interactive example,
you'll notice that the else clause is indented to the same level as the
for statement.  This means that the statements in the else block will be
executed if the for loop is allowed to run to completion (no break is
encountered).

In the example you entered in gvim, the else clause is indented to the
level of the if statement so it will be executed whenever the if test
fails during a pass through the loop - giving you incorrect results.

I hope this explanation is somewhat clear.  Good luck with the rest of
the tutorial!

On Tue, 2003-07-01 at 13:37, Chris Readle wrote:
> Hi all, 
> 
> My name is Chris and I've just started learning Python.  I'm working
> through the tutorial and I've come upon a difficult thing.  One of the
> sample pieces of code works fine when typed interactively into the
> interpreter, but doesn't seem to work when I type it up in gvim.  Here are
> the two bits of code:
> 
> Bit that works:
> for n in range(2,10):
>     for x in range(2, n):
>         if n % x == 0:
>             print n, 'equals', x, '*', n/x
>             break
>     else:
>         # Loop fell through without finding factor
>         print n, 'is a prime number'
> 
> This bit returns:
> 2 is a prime number
> 3 is a prime number
> 4 equals 2 * 2
> 5 is a prime number
> 6 equals 2 * 3
> 7 is a prime number
> 8 equals 2 * 4
> 9 equals 3 * 3
> 
> Which the tutorial indicates is correct.
> 
> 
> Bit that doesn't work:
> # Testing to see if there is some funny starting value in the variables
> causing this to fail
> n, x = 0, 0
> print n, x
> 
> for n in range(2,10):
> 	for x in range(2, n):
> 		if n % x == 0:
> 			print n, 'equals', x, '*', n/x
> 			break
> 		else:
> 			# Loop fell through without finding a factor
> 			print n, 'is a prime number'
> 
> This bit returns:
> 0 0
> 3 is a prime number
> 4 equals 2 * 2
> 5 is a prime number
> 5 is a prime number
> 5 is a prime number
> 6 equals 2 * 3
> 7 is a prime number
> 7 is a prime number
> 7 is a prime number
> 7 is a prime number
> 7 is a prime number
> 8 equals 2 * 4
> 9 is a prime number
> 9 equals 3 * 3
> 
> Which is a little messed.
> 
> Now, the only thing I see that's different is that they're indented
> differently.  However, both are indented consistently, which is my
> understanding of how that should work.  To add some kick to the sauce, if
> I take the former example and paste it into a text file and run THAT
> through the interpreter, it works as well.
> 
> Any thoughts from the python experts out there?
> 
> chris
> 
> 
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-- 
Reggie