ConvertCsvtoSvmLight.py

#!/usr/bin/env python

"""
Convert CSV file to libsvm format. Works only with numeric variables.
Put -1 as label index (argv[3]) if there are no labels in your file.
Expecting no headers. If present, headers can be skipped with argv[4] == 1.
"""

import sys
import csv
from collections import defaultdict

def construct_line( label, line ):
	new_line = []
	if float( label ) == 0.0:
		label = "0"
	new_line.append( label )

	for i, item in enumerate( line ):
		if item == '' or float( item ) == 0.0:
			continue
		new_item = "%s:%s" % ( i + 1, item )
		new_line.append( new_item )
	new_line = " ".join( new_line )
	new_line += "\n"
	return new_line

# ---

input_file = sys.argv[1]
output_file = sys.argv[2]

try:
	label_index = int( sys.argv[3] )
except IndexError:
	label_index = 0

try:
	skip_headers = sys.argv[4]
except IndexError:
	skip_headers = 0

i = open( input_file, 'rt' )
o = open( output_file, 'wt' )

reader = csv.reader(i)

if skip_headers:
	headers = next(reader, None)

for line in reader:
	if label_index == -1:
		label = '1'
	else:
		label = line.pop( label_index )

	new_line = construct_line( label, line )
	o.write( new_line )