Calculate Prime Numbers in Python

prime0020.py

''' calculate prime numbers '''

DEBUG = False
HIGH_NUMBER = 2000

# initial list of primes contains only the number 2.
known_primes = [ 2 ]

for n in range(known_primes[0]+1,HIGH_NUMBER,2):
    if DEBUG:
        print(" -------------- %d", n)
    a = n
    for p in known_primes:
        # first prime which divides evenly disqualifies n as prime
        if n % p == 0:
            a = None
            if DEBUG:
                print('Note: %d is not prime (divisible by prime %d)' % (n, p))
            break
    if a is not None:
        known_primes.append(a)

print(known_primes)