Prime number finder - optimization

Question

I\'m trying to build a prime number finder that would work as fast as possible. This is the def function that is included in the program. I\'m having problems with just one deta

Answer 1

As pointed out in the comment above, python2 performs integer division so 1/2 == 0

• You can write your root as:

  x**0.5
  

• or using math.sqrt:

  math.sqrt(x)
  

The naive primality test can be implemented like this:

def is_prime(n):
    if n<=1: return False
    if n<=3: return True
    if not n%2 or not n%3: return False
    i=5
    while i*i<=n:
        if n%i==0: return False
        i+=2
        if n%i==0: return False
        i+=4
    return True