csvfile = check_csv_file(ifile)

$ python check_csv_file.py jj.xls
Creating jj.csv from jj.xls
Input name jj.xls, output name jj.csv

$ python check_csv_file.py jj.xls
Input name jj.xls, output name jj.csv

$ python check_csv_file.py jj.csv
Input name jj.csv, output name jj.csv

$ touch jj.xls
$ python check_csv_file.py jj.csv
Recreating jj.csv from jj.xls
Input name jj.csv, output name jj.csv

import os
import re
import sys
import csv


def check_csv_file(csvfile):
    """
    Make sure the CSV file exists.
    If it does not exist, try to create it from an XLS or ODS file.
    The passed name can refer to an XLS file or an ODS file.
    The return value will be the name of a CSV file.
    """
    def find_csv(csvf):
        """ Check to see if the CSV file exists. """
        fname, ext = os.path.splitext(csvf)
        ext        = ext.lower()
        if   ext == '.txt':
            f = '%s.%s' % (fname, 'TXT')
            if os.path.exists(f):
                csvf = f
            else:
                csvf = '%s.%s' % (fname, 'txt')

        elif ext != '.csv':
            f = '%s.%s' % (fname, 'CSV')
            if os.path.exists(f):
                csvf = f
            else:
                csvf = '%s.%s' % (fname, 'csv')

        return csvf

    def find_sheet(ssvf):
        """ Check to see if the spread sheet file exists. """
        sheetf = None
        fname  = os.path.splitext(ssvf)[0]
        for ext in ('xls', 'XLS', 'ods', 'ODS'):
            f = '%s.%s' % (fname, ext)
            if os.path.exists(f):
                sheetf = f
                break

        return sheetf

    def convert_sheet(sheetf, csvf):
        """ Convert spreadsheet to a CSV file. """
        import ooutils
        from ssconverter import SSConverter
        try:
            converter = SSConverter()
            converter.convert(sheetf, csvf)
        except Exception, e:
            sys.stderr.write("ERROR: %s\n" % e.message)
            sys.exit(1)

    # Find the spreadsheet file that corresponds to the CSV file
    csvfile   = find_csv(csvfile)
    sheetfile = find_sheet(csvfile)

    if sheetfile:
        # If CSV does not exist try to create it.
        if not os.path.exists(csvfile):
            sys.stderr.write("Creating %s from %s\n" % (csvfile, sheetfile))
            convert_sheet(sheetfile, csvfile)
        else:
            # If spreadsheet is newer the CSV file, re-create it.
            if os.stat(csvfile).st_mtime < os.stat(sheetfile).st_mtime:
                sys.stderr.write("Recreating %s from %s\n" % (csvfile, sheetfile))
                convert_sheet(sheetfile, csvfile)


    if not os.path.exists(csvfile):
        sys.stderr.write('File not found: %s\n' % csvfile)
        sys.exit(1)

    return csvfile


if __name__ == "__main__":
    for f in sys.argv[1:]:
        f2 = check_csv_file(f)
        print "Input name %s, output name %s" % (f, f2)