Prime python.

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#1
I was wondering if there was a simple way to see if a number is prime in python 3.3.3 or whether I need to do a big loop with decreasing numbers and check them against the original number.
0
6 years ago
#2
(Original post by SamRob85)
I was wondering if there was a simple way to see if a number is prime in python 3.3.3 or whether I need to do a big loop with decreasing numbers and check them against the original number.
If you were to find one, you would make a lot of money.

Check for factors between 2 and the (rounded up if necessary) square root of the number, and if it doesn't have any then you can be certain it's prime. This isn't feasible for huge numbers but I'm assuming you're not using huge numbers.
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#3
If you were to find one, you would make a lot of money.

Check for factors between 2 and the (rounded up if necessary) square root of the number, and if it doesn't have any then you can be certain it's prime. This isn't feasible for huge numbers but I'm assuming you're not using huge numbers.
Would I be able to miss out 6 if I did 3 as it is a multiple of it?
0
6 years ago
#4
(Original post by SamRob85)
Would I be able to miss out 6 if I did 3 as it is a multiple of it?
Sorry I thought I put this in my first post, check 2 outside the loop then for the loop make the 'step' 2 so it only checks odd numbers.
0
6 years ago
#5
(Original post by SamRob85)
I was wondering if there was a simple way to see if a number is prime in python 3.3.3 or whether I need to do a big loop with decreasing numbers and check them against the original number.
You would need to determine if a positive integer , is a prime number if it is not evenly divisible by any other integers other than 1 and itself. I stopped learning python for the time being so I cant show you an example based off the language but I can give you understanding of how algorithm should have to function.

Code:
```// Program to generate a table of prime numbers

#import <Foundation/Foundation.h>

int main (int argc, char * argv[])

{

@autoreleasepool {

int p, d, isPrime;

for ( p = 2; p <= 50; ++p ) {

isPrime = 1;

for ( d = 2; d < p; ++d )

if ( p % d == 0 )

isPrime = 0;

if ( isPrime != 0 )

scanf ("%i ", p);

}
}
return 0;
}```
0
6 years ago
#6
(Original post by Grecko)
You would need to determine if a positive integer , is a prime number if it is not evenly divisible by any other integers other than 1 and itself. I stopped learning python for the time being so I cant show you an example based off the language but I can give you understanding of how algorithm should have to function.

Code:
```// Program to generate a table of prime numbers

#import <Foundation/Foundation.h>

int main (int argc, char * argv[])

{

@autoreleasepool {

int p, d, isPrime;

for ( p = 2; p <= 50; ++p ) {

isPrime = 1;

for ( d = 2; d < p; ++d )

if ( p % d == 0 )

isPrime = 0;

if ( isPrime != 0 )

scanf ("%i ", p);

}
}
return 0;
}```
OP didn't want to generate primes, he wanted an algorithm to determine whether a given number was prime.
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