Question

PS 1a

I am attempting to complete PS 1a. I got it to work the LONG way (manually checking each division and concatenating result). I was trying to get a bit more efficient and automatically calculate each division, but I can't get it to work. Any suggestions? My code is below:
x=2
count=0
count_max=1000
while count 11 years ago

Answer 1

i tweaked it and put in some comments but didn't test it
http://dpaste.com/740808/

Answer 2

Here's another way to do it: http://pastebin.com/4FgBPcq8
Also, in@ bwCA 's function, it can be a bit faster if you start with 5 instead and increament x by 2 instead of 1.

Answer 3

You have a problem with your inner while loop:

while y > 1:
if x % y == 0:
# not prime - stop checking
#count=count
break
else:
y = y - 1
if y == 1:
#if you got here it must be prime
count = count + 1 *********

The problem is that you will not be able to execute the part where I marked *********. This is because the condition of your while loop is "while y>1". Therefore, the result of "if y == 1" inside this while loop will always be False since all the y's that are tested here are all greater than 1. Hence, count = count + 1 will never be executed. My suggestion is to take this "if" block outside of the while loop since after the while loop finishes, the value of y is surely 1 if it is prime.

Go test it. You have to add some more lines to make it work but you have to figure that out on your own. :)