Save a PyGame drawing

''' pg_draw_circle_save101.py
draw a blue solid circle on a white background
save the drawing to an image file
for result see http://prntscr.com/156wxi
tested with Python 2.7 and PyGame 1.9.2 by vegaseat  16may2013
'''

import pygame as pg

# pygame uses (r, g, b) color tuples
white = (255, 255, 255)
blue = (0, 0, 255)

width = 300
height = 300

# create the display window
win = pg.display.set_mode((width, height))
# optional title bar caption
pg.display.set_caption("Pygame draw circle and save")
# default background is black, so make it white
win.fill(white)

# draw a blue circle
# center coordinates (x, y)
center = (width//2, height//2)
radius = min(center)
# width of 0 (default) fills the circle
# otherwise it is thickness of outline
width = 0
# draw.circle(Surface, color, pos, radius, width)
pg.draw.circle(win, blue, center, radius, width)

# now save the drawing
# can save as .bmp .tga .png or .jpg
fname = "circle_blue.png"
pg.image.save(win, fname)
print("file {} has been saved".format(fname))

# update the display window to show the drawing
pg.display.flip()

# event loop and exit conditions
# (press escape key or click window title bar x to exit)
while True:
    for event in pg.event.get():
        if event.type == pg.QUIT:
            # most reliable exit on x click
            pg.quit()
            raise SystemExit
        elif event.type == pg.KEYDOWN:
            # optional exit with escape key
            if event.key == pg.K_ESCAPE:
                pg.quit()
                raise SystemExit