#!/usr/bin/python
# Count charge of polypeptide as in [1]
# (c) 2008 Tobias Abenius, licence: GPL
# 1. Yu Shi, Coreceptor Usage and Sensitivity to Neutralization of HIV-1 & HIV-2
from sys import argv, stderr, exit

def count(cond,l):
	return sum(map(cond,l))

def charge(seq):
	seq = seq.lower()
	positive = lambda c: c in 'rk'
	negative = lambda c: c in 'ed'
	return count(positive,seq) - count(negative,seq)

if __name__ == "__main__":
	if len(argv) != 2:
		stderr.write("Syntax: %s <file>" % argv[0])
		exit(1)
	stderr.write("Reading sequences separated by newline from file '%s'\n" % argv[1])
	for row in file(argv[1]).readlines():
		print charge(row)