Sift3 in Python

sift3.py

def sift3(s1,s2, maxOffset):
	s1L = len(s1)
	s2L = len(s2)
	if not s1:
		return (not s2 and 0 or s2L)
	if not s2:
		return s1L
	c1 = 0
	c2 = 0
	lcs = 0
	while c1<s1L and c2<s2L:
		if s1[c1] == s2[c2]:
			lcs += 1
		else:
			for i in range(1,maxOffset):
				if c1+i < s1L and s1[c1+i] == s2[c2]:
					c1 += i
					break
				if c2+i < s2L and s1[c1] == s2[c2+i]:
					c2 += i
					break
		c1 += 1
		c2 += 1
	return ((s1L+s2L)/2-lcs)