basic python question about for loop

[Reedick, Andrew]

> -----Original Message-----
> From: python-list-bounces+jr9445=att.com at python.org [mailto:python-
> list-bounces+jr9445=att.com at python.org] On Behalf Of jmDesktop
> Sent: Wednesday, April 09, 2008 4:51 PM
> To: python-list at python.org
> Subject: basic python question about for loop
> 
> >From the Python.org tutorial:
> 
> >>> 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'
> ...
> 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
> 
> 
> 
> first time 2 mod 2, 2/2, no remainder == 0, what am I doing wrong?
> Why did it fall through?
> 

a) 2 is prime, so nothing is wrong.

b) Range isn't doing what you think it's doing:

>>> print range(2,2)
[]
>>> print range(2,3)
[2]
>>> print range(2,4)
[2, 3]
>>> print range(2,5)
[2, 3, 4]

>>> print range(1,1)
[]
>>> print range(1,2)
[1]
>>> print range(1,3)
[1, 2]
>>>



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