素数を数え上げるプログラム（試し割り法）

primenumber.py

import math

primenumber = []
checkTarget = 2

while True:
	isPrime = True
	sqrtTarget = math.sqrt(checkTarget)
	for x in primenumber:
		if (checkTarget % x) == 0:
			isPrime = False
			break
		if x > sqrtTarget:
			break
	if isPrime:
		primenumber.append(checkTarget)
		print(str(checkTarget) + " is prime number. " 
			+ "#" + str(len(primenumber)))   
	checkTarget = checkTarget + 1