import media

def get_picture():
    '''Let the user select a picture file, get the picture, and return it'''
    
    filename = media.choose_file()
    pic = media.load_picture(filename)
    return pic
    
def make_sunset (pic):
    '''Change picture pic so that it looks like it was taken at sunset'''

    # Reduce the blue and green by 30% each to make
    # the red stand out.
    for pixel in pic:
        green = media.get_green(pixel) 
        media.set_green(pixel, int(green * 0.7)) 

        blue = media.get_blue(pixel) 
        media.set_blue(pixel, int(blue * 0.7))
    print 'Set a breakpoint here so we can stop and look at variables'
    
if __name__ == '__main__':
    a = get_picture()
    b = a
    make_sunset(a)
    media.show(b)
    # a and b still refer to the same picture object, 
    # but something about it has changed