bouncing

#!/usr/bin/env python3
# Print a bouncing O. Pretty much the most pointless script ever.

import sys
import time
import os


width = os.get_terminal_size().columns

def display_line(index, width, stream=None):
    if index >= width:
        raise IndexError('index %r should be < width %r' % (index, width))
    if index < 0:
        raise IndexError('index %r is < 0' % index)

    if stream is None:
        stream = sys.stdout

    stream.write('\r')
    for i in range(width):
        if i == index:
            stream.write('O')
        else:
            stream.write(' ')
    stream.flush()

def sleep():
    time.sleep(0.05)

def main():
    while True:
        for x in range(width):
            display_line(index=x, width=width)
            sleep()
        for x in range(width-1, 0, -1):
            display_line(index=x, width=width)
            sleep()

if __name__ == '__main__':
    try:
        main()
    except KeyboardInterrupt:
        sys.stderr.write('\n')