Shell Programming and Scripting

I have written a small practice Python script to determine the prime numbers between 2-10, for practice. Although I have pored over this script numurous times, I have not found the problem.

The problem is: Python will not print "is a prime" when a number is a prime. After examining the code below, this will make sense..

Code:

for i in range(2,10):
	print
	print i,"-",
	for j in range(2,i):
		if (i % j) == 0:
			print j,
		else:
			if j == i + 1:
				print "is a Prime"

On execution, it prints this:

Code:

2 -
3 -
4 - 2
5 -
6 - 2 3
7 -
8 - 2 4
9 - 3

Note:I am using the Windows 98 IDLE GUI. I am not sure if this is affecting it..

I believe line 8 may be a problem. I am not sure whether to use "j - 1 == i" or j == i + 1".

Thank you,
Furtoes00

First - I have no idea what Python is.
Second - that means I have no idea of it's syntax.

BUT -

As Spock would say "Logic suggest..."

This code you posted:

if (i % j) == 0:
print j,
else:
if j == i + 1:
print "is a Prime"


IF it prints j, you will never go to the else. Logic is logic -

if (true) then do this ELSE do this - you need to change this so it looks at each separately or looks at the second within the if

if (true) then
print j
if (true) then
print "is a Prime"

That does make sense; here is the modified code:

Code:

for i in range(2,10):
	print
	print i,"-",
	for j in range(2,i):
		if (i % j) == 0:
			print j,
		if j == i + 1:
			print "is a Prime"

However, that does not work, either!!

I too do not know python. But it looks like you line "for j in range(2,i)" will vary j starting at 2 and going up to either i or i-1, I'm not sure which from this thread. But either way, it looks like your final test in the loop is to see if j equals i+1. How can that ever happen?

In any event, your problem isn't python, it's the algorithm. Your inner loop is finding factors. Before you enter that inner loop, set "nfactor=0". Each time you find a factor and do the "print j", also increment nfactor. After the inner loop finishes, test nfactor...if it's zero, "print prime".

I tried that before; it didn't work. Neither

i++

nor

i += 1

nor

i = i + 1

works.