def count_nonsyn(mvf_file):
	"""
	count number of nonsynonymous variants from mvf file
	"""
	ns_num = 0
	for line in mvf_file:
		line = line.rstrip()
		if ':' not in line: continue
		codon = line.split(' ')[1]
		if len(codon) > 1:
			ns_num += 1
	return ns_num