Question

hello, can someone plz tell me why this loop wont stop after finding the 10 first prime numbers?

p=3
n=0
while (n<10):
for a in range (1,999999):
if(a**(p-1)-1)%p == 0:
print p
p=p+2
n=n+1

Answer 1

get the n=n+1 line inside the while loop...it will stop..
for now...n never increases from 0 , because n=n+1 is outside the while loop...so it is an infinite loop

Answer 2

so, do you mean like this:
p=3
n=0
while (n<10):
for a in range (1,999999):
if(a**(p-1)-1)%p == 0:
print p
p=p+2
n=n+1
because that do not work

Answer 3

that won't coz it's inside the for loop..
try it like this

p=3
n=0
while (n<10):
for a in range (1,999999):
if(a**(p-1)-1)%p == 0:
print p
p=p+2
n=n+1
because that do not work
i'm not sure about your prime number method though..

Answer 4

No, he meant

p=3
n=0
while (n<10):
for a in range (1,999999):
if(a**(p-1)-1)%p == 0:
print p
p=p+2
n=n+1

Blocks in python works by indentation. So if it's in a different level of indentation, it has a different meaning.

Answer 5

i found the method on wikipedia, but are you sure its like that. because when i run it like you show then it still keep on going past the 10th prime. sry for asking alot of questions but i am totally new to programming...

Answer 6

try this
p=3
n=0
while (n<10):
for a in range (1,99):
if(a**(p-1)-1)%p == 0 and n<10:
print p
n=n+1
p=p+2

Answer 7

great, thanks :D but why did that work? is it not more intuitive to first write p=p+2 and then n=n+1?

Answer 8

notice i shortened the range...and the other thing the while loop is not checking for n here before the print actually...because it never exits for loop till it gets to the upper range..so u have to perform the check inside the for loop and therefore the increment has to be inside for loop too..
i am not any good at explaining things..
Lifeburner is pretty good at it though :)

Answer 9

At a glance, there are 2 possible problems there:

1) Like sunu pointed out, 99999 is just too big.
2) If I understand correctly, a is your divisor? If so, instead of just picking a very large upper limit, try setting a logical limit instead.