[Tutor] Else Clause In A Loop

[Alan Gauld]

"kinuthia muchane" <muchanek at gmail.com> wrote

> This has served to confuse me more. Would someone please kindly 
> explain
> how all this fits into the code below which searches (and finds!) 
> for
> prime numbers...

It doesn't find prime numbers very well.
It only finds the primes *below* the one entered.
So...

> def prime():
>   number = int(raw_input("Enter a number :"))
>   for i in range(2,number):
>      for j in range(2,i):
>         if i%j == 0:
>             break
>       else:
>         print "is a prime number", i
>
> prime()
>
> ...especially in the instance when number is 2 in the first for
> statement, for then we will have for j range(2,2)!

When number is 2 it doesnm't print anything. Which as you point
out is as you would expect since the first range() will be empty.

For number=3 the first range has one element so it enters the
second loop with an empty list so goes straight to the else
clause.

I'm not a sure what you are confused about?
The code is not very elegant or effective but it does what you
have described in your experiments.


-- 
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld