Explanation of script

[swappo1]

Hello,

I am running a script for a tutorial and I don't quite understand what is happening.

I have added a print n statement below the for n...statement and print x below the for x...statement to help understand what is happening.

#! /usr/bin/env python
# using_break_statement.py

for n in range(2, 10):
print n
for x in range(2, n):
print x
if n % x == 0:
print n, "equals", x, "*", n/x
break
else:
print n, "is a prime number"
I get the following output

scott@scott-laptop:~$ python using_break_statement.py
2
2 is a prime number
3
2
3 is a prime number
4
2
4 equals 2 * 2
5
2
3
4
5 is a prime number
6
2
6 equals 2 * 3
7
2
3
4
5
6
7 is a prime number
8
2
8 equals 2 * 4
9
2
3
9 equals 3 * 3

x does not seem to be incrementing like I would expect. After n = 4 it prints out two numbers for n and x? I think I am not understanding how the second range function is working. Thanks for any help.

[ghostdog74]

indent your last print statement.

[swappo1]

Here is a repost of the script. It seems the formatting changed when I pasted it in.

for n in range(2, 10):
print n
for x in range(2, n):
print x
if n % x == 0:
print n, "equals", x, "*", n/x
break
else:
print n, "is a prime number"

[ghostdog74]

your else is "orphaned".

[dribeas]

Here is a repost of the script. It seems the formatting changed when I pasted it in.

for n in range(2, 10):
print n
for x in range(2, n):
print x
if n % x == 0:
print n, "equals", x, "*", n/x
break
else:
print n, "is a prime number"
What is going on in the code is that x is being incremented up to the point where factors are found. Then you break out of the inner for (x), and in the next iteration of the outer for (n) you start again with x = 2. The inner loop iterates from 2 to either n/2 if n is prime or the first factor of n. As you are breaking out of the inner for, the else statement does not get executed.