filter-abund.py

#! /usr/bin/env python
"""
Trim sequences at k-mers of the given abundance, based on the given counting
hash table.  Output sequences will be placed in 'infile.abundfilt'.

% python scripts/filter-abund.py <counting.kh> <data1> [ <data2> <...> ]

Use '-h' for parameter help.
"""
import sys, screed.fasta, os
import khmer
from khmer.thread_utils import ThreadedSequenceProcessor, verbose_loader

from khmer.counting_args import build_counting_multifile_args

###

DEFAULT_CUTOFF=2

def main():
    parser = build_counting_multifile_args()
    parser.add_argument('--cutoff', '-C', dest='cutoff',
                        default=DEFAULT_CUTOFF, type=int,
                        help="Trim at k-mers below this abundance.")
    args = parser.parse_args()

    counting_ht = args.input_table
    infiles = args.input_filenames

    print 'file with ht: %s' % counting_ht

    print 'loading hashtable'
    ht = khmer.load_counting_hash(counting_ht)
    K = ht.ksize()

    print "K:", K

    ### the filtering function.
    def process_fn(record):
        name = record['name']
        seq = record['sequence']
        if 'N' in seq:
            return None, None

        trim_seq, trim_at = ht.trim_on_abundance(seq, args.cutoff)

        if trim_at >= K:
            return name, trim_seq

        return None, None


    ### the filtering loop
    for infile in infiles:
       print 'filtering', infile
       outfile = os.path.basename(infile) + '.abundfilt'
       outfp = open(outfile, 'w')

       tsp = ThreadedSequenceProcessor(process_fn)
       tsp.start(verbose_loader(infile), outfp)

       print 'output in', outfile

if __name__ == '__main__':
    main()