import os py26 = r'C:\Python26\\' py30 = r'C:\Python30\\' textfile = 'large.txt' binaryfile = 'large.bin' os.system('%s\python timeIO.py %s %s' % (py26, textfile, binaryfile)) os.system('%s\python timeIO.py %s %s' % (py30, textfile, binaryfile))