‘tuple’ object does not support item assignment

I am using the PIL library.

I am trying to make an image look red-er, this is what i’ve got.

from PIL import Image
image = Image.open('balloon.jpg')
pixels = list(image.getdata())
for pixel in pixels: 
    pixel[0] = pixel[0] + 20    

However I get this error: TypeError: 'tuple' object does not support item assignment

6 Answers

PIL pixels are tuples, and tuples are immutable. You need to construct a new tuple. So, instead of the for loop, do:

pixels = [(pixel[0] + 20, pixel[1], pixel[2]) for pixel in pixels]

Also, if the pixel is already too red, adding 20 will overflow the value. You probably want something like min(pixel[0] + 20, 255) or int(255 * (pixel[0] / 255.) ** 0.9) instead of pixel[0] + 20.

And, to be able to handle images in lots of different formats, do image = image.convert("RGB") after opening the image. The convert method will ensure that the pixels are always (r, g, b) tuples.

The second line should have been pixels[0], with an S. You probably have a tuple named pixel, and tuples are immutable. Construct new pixels instead:

image = Image.open('balloon.jpg')

pixels = [(pix[0] + 20,) + pix[1:] for pix in image.getdata()]


Tuples, in python can’t have their values changed. If you’d like to change the contained values though I suggest using a list:

[1,2,3] not (1,2,3)

You probably want the next transformation for you pixels:

pixels = map(list, image.getdata())

A tuple is immutable and thus you get the error you posted.

>>> pixels = [1, 2, 3]
>>> pixels[0] = 5
>>> pixels = (1, 2, 3)
>>> pixels[0] = 5
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment

In your specific case, as correctly pointed out in other answers, you should write:

pixel = (pixel[0] + 20, pixel[1], pixel[2])

You have misspelt the second pixels as pixel. The following works:

pixels = [1,2,3]
pixels[0] = 5

It appears that due to the typo you were trying to accidentally modify some tuple called pixel, and in Python tuples are immutable. Hence the confusing error message.

Leave a Reply

Your email address will not be published. Required fields are marked *