#format python

"""ReverseComplement using BioPython
"""

import sys
from Bio import Fasta

dictDnaComp = {'A':'T', 'T':'A', 'G':'C', 'C':'G'}

def main(infilename, outfilename):
    try:
        infile = open(infilename, 'r')
        outfile = open(outfilename, 'w')
    except:
        print "Error: unable to open file"
        sys.exit()
    parser = Fasta.RecordParser()
    iterator = Fasta.Iterator(infile, parser)
    while 1:
        curRecord = iterator.next()
        if curRecord is None: break
        curRecord.sequence = convert(curRecord.sequence)
        outfile.write(str(curRecord))

def convert(aSeq):
    newSeq = ''
    for index in range(len(aSeq)-1, -1, -1):
        newSeq += dictDnaComp[aSeq[index]]
    return newSeq

if __name__ == '__main__': 
    ifile, ofile = sys.argv[1:3]
    main(ifile, ofile)