#!/usr/bin/python2.6

"""
Read a MAF from standard input and print average GC content of each alignment

usage: %prog < maf > out
"""

from __future__ import division

import sys

from bx.align import maf


def __main__():
    
    maf_reader = maf.Reader( sys.stdin )

    for m in maf_reader:
        gc = 0
        bases = 0
        for c in m.components:
          gc += c.text.count( 'G' )
          gc += c.text.count( 'C' )
          gc += c.text.count( 'g' )
          gc += c.text.count( 'c' )
          bases += ( len( c.text ) - c.text.count( '-' ) )

        print gc / bases

if __name__ == "__main__": __main__()
