Sieve Of Eratosthenes in python

primesieve.py

import math

class SieveOfEratosthenes(object):
	def __init__(self, limit1, limit2 = None):
		if limit2 is None:
			self.lowerLimit = 2
			self.upperLimit = limit1
		else:
			if limit1 <= 1:
				raise RuntimeError("Lower limit must be at least 2")
			self.lowerLimit = limit1
			self.upperLimit = limit2 

		self.vals = set(range(self.lowerLimit, self.upperLimit))
		iLim = math.ceil(self.upperLimit ** 0.5)

		#Remove even numbers
		i = 2
		m = i+i #First multiple of 2
		if self.lowerLimit > m:
			m = (self.lowerLimit // i) * i
		while m < self.upperLimit:
			try:
				self.vals.remove(m)
			except KeyError:
				pass
			m += i

		#Only process odd numbers from here
		i = 3
		while i <= iLim:
			m = i+i #First multiple of i
			if self.lowerLimit > m:
				m = (self.lowerLimit // i) * i
			while m < self.upperLimit:
				try:
					self.vals.remove(m)
				except KeyError:
					pass
				m += i
			i += 2

if __name__=="__main__":
	soe = SieveOfEratosthenes(104730)
	print "Found", len(soe.vals), "primes"

	#Validate against first 10000 primes https://primes.utm.edu/lists/small/10000.txt
	primes = set()
	fi = open("10000.txt", "rt")
	for i in range(4):
		fi.readline()
	for li in fi.readlines():
		if li.strip() == "end.": break
		primes.update([int(val.strip()) for val in li.strip().split()])	

	#primes = set([p for p in primes if p > ii])

	if primes != soe.vals:
		print "Mismatch"
		print "Missing:", primes.difference(soe.vals)
		print "Extra:", soe.vals.difference(primes)
	else:
		print "All good!"