svm-remap.py

#!/usr/bin/env python3

"""Remap SVM target of every line from one numeric target to another
based on the name file of every target.
@author Dat Hoang
@date March 2011"""

import sys
import csv
from optparse import OptionParser


FIELD_DELIMITER='\t'
SVM_DELIMITER=' '


def gen_remap_table(from_fp, to_fp):
    """Generate a hash table to remap category names between SVM files."""
    freader = csv.reader(from_fp, delimiter=FIELD_DELIMITER)
    treader = csv.reader(to_fp, delimiter=FIELD_DELIMITER)
    
    ftable = dict((i, field) for i, field in freader)
    ttable = dict((field, i) for i, field in treader)

    return dict((i, ttable[field]) for i, field in ftable.items())

def svm_remap(remap_table, in_fp, out_fp):
    """Remap all category integers according to remap table."""
    def remap(category):
        return remap_table[category]

    reader = csv.reader(in_fp, delimiter=SVM_DELIMITER)
    for line in reader:
        category, *rest = line
        out_fp.write("%s%s%s\n" % (
            remap(category), SVM_DELIMITER, SVM_DELIMITER.join(rest)))

def main():
    parser = OptionParser(
        usage="""Usage: %prog <from-fields> <to-fields> <in-svm> <out-svm>
            <from-fields> := file of fields to map from
            <to-fields> := file of fields to map to
            <in-svm> := input SVM file to remap ( - := /dev/stdin)
            <out-svm> := output SVM file ( - := /dev/stdout)""")
    (_, args) = parser.parse_args()
    if len(args) != 4:
        parser.print_usage(file=sys.stderr)
        return 1
    
    from_fields = args[0]
    to_fields = args[1]
    svm_in = "/dev/stdin" if args[2]=='-' else args[2]
    svm_out = "/dev/stdout" if args[3]=='-' else args[3]

    with open(from_fields, 'r') as from_fp, open(to_fields, 'r') as to_fp:
        remap_table = gen_remap_table(from_fp, to_fp)

    with open(svm_in, 'r') as in_fp, open(svm_out, 'w') as out_fp:
        svm_remap(remap_table, in_fp, out_fp)

    return 0

if __name__=="__main__":
    sys.exit(main())