primes

#!/usr/bin/env python3

import os, sys

def main(args=None):
	import argparse
	parser = argparse.ArgumentParser(
		description='Print prime numbers in specified range, one per line, if any.')
	parser.add_argument('n_min', type=int, help='Number range start.')
	parser.add_argument('n_max', nargs='?', type=int, help='Number range end.')
	parser.add_argument('-a', '--all', action='store_true',
		help='Print all primes within range, not just the first one.')
	opts = parser.parse_args(sys.argv[1:] if args is None else args)

	a, b, one = opts.n_min, opts.n_max, not opts.all
	if not b: one, b = True, a + 1000
	if not a % 2: a += 1

	for n in range(a, b, 2): # skips most common factor
		for x in range(3, int(n**0.5) + 1): # n = x*y, so min(x, y) <= sqrt(n)
			if not n % x: break
		else:
			print(n)
			if one: break

if __name__ == '__main__': sys.exit(main())