My handling of exceptions and sys.exit()

Segmentor.py

    def __init__(self, filename, slice_length):
        try:
            self.file = open(filename, 'r')
            self.slice_length = int(slice_length)
        except IOError, e:
            print "No such file:", sys.argv[1]
            sys.exit()
        except ValueError, e:
            print "\"%s\" isn't a number." % sys.argv[2]
            print "Usage: Segmentor.py <file> <slice length>"
            sys.exit()