pillow reversing the order of pixels after every row

[scidam]

The pixels variable has shape 32x32x3, it is a numpy array. You can easily manipulate with numpy arrays without pure-Python loops; If you want to invert all rows of the image, just do:

inverted = pixels[:, ::-1, :]

If you want to invert all odd rows, do

inverted = pixels.copy()
inverted[::2,...] = inverted[::2, ::-1, :]
# now inverted var. has desired form