#!/usr/bin/python2.6

"""
Read a maf from stdin and print the chromosome number for each alignment. It
searches for 'chr' in each alignment block src, and may not be robust if other
src formats are used. 

NOTE: See 'align_print_template.py' for a more general variation of this
      program.

usage: %prog refindex [options]
"""

from __future__ import division

import sys
from bx.cookbook import doc_optparse
from bx.align import maf
from optparse import OptionParser

def __main__():

    # Parse command line arguments
    options, args = doc_optparse.parse( __doc__ )

    try:
        refindex = int( args[0] )
    except:
        doc_optparse.exit()

    maf_reader = maf.Reader( sys.stdin )

    for m in maf_reader: 
		c = m.components[ refindex ].src
		print c[ c.rfind( "chr" ) + 3 : ]

if __name__ == "__main__": __main__()
