SyntaxError: can't assign to expression出错误报出如何解决，求大神帮忙

[k1h5]

import sensor, image, time, math

sensor.reset()                      # Reset and initialize the sensor.
sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.VGA)   # Set frame size to QVGA (320x240)
sensor.skip_frames(time = 2000)     # Wait for settings take effect.
clock = time.clock()                # Create a clock object to track the FPS.

while(True):
    #img = sensor.snapshot()         # Take a picture and return the image.
    img = sensor.snapshot()
    #红色阈值
    for y in range(0,480,3):
        for x in range(0,640):
            #img.get_pixel(x,y)
            if img.get_pixel(x,y)>=205:
               img.get_pixel(x,y)=255
            elif img.get_pixel(x,y)<=195:
               img.get_pixel(x,y)=0
            else:
               img.get_pixel(x,y)=img.get_pixel(x,y)

[kidswong999]

img.get_pixel(x,y)=0

get_pixel返回的具体的数值，不能直接赋值，要用set_pixel赋值。