AttributeError: module 'PIL.Image' has no attribute 'Resampling'

The error, reproduced on Pillow 9.0.1

We keep a Python 3.10 environment with Pillow 9.0.1 to reproduce errors from old installs. The same script on the old and the current Pillow:

from PIL import Image

img = Image.open("photo.jpg")
small = img.resize((400, 267), Image.Resampling.LANCZOS)
print(small.size)

Traceback (most recent call last):
  ...
AttributeError: module 'PIL.Image' has no attribute 'Resampling'

from PIL import Image

img = Image.open("photo.jpg")
small = img.resize((400, 267), Image.Resampling.LANCZOS)
print(small.size)

(400, 267)

What changed in Pillow 9.1

Pillow 9.1 (April 2022) grouped its integer constants into enums: Image.Resampling, Image.Transpose, Image.Dither, Image.Palette, Image.Quantize and Image.Transform. On the older version, none of them exist:

import PIL
from PIL import Image

print("Pillow", PIL.__version__)
for name in ["Resampling", "Transpose", "Dither", "Palette", "Quantize", "Transform"]:
    print(f"  Image.{name:<11}", "yes" if hasattr(Image, name) else "missing")
print("  Image.LANCZOS    ", Image.LANCZOS)

Pillow 9.0.1
  Image.Resampling  missing
  Image.Transpose   missing
  Image.Dither      missing
  Image.Palette     missing
  Image.Quantize    missing
  Image.Transform   missing
  Image.LANCZOS     1

So the same error appears as has no attribute 'Transpose' for code that flips or rotates with Image.Transpose.FLIP_LEFT_RIGHT, and so on. The fix is identical.

Find out why the old Pillow is there

Check the version the failing interpreter actually uses: python -c "import PIL; print(PIL.__version__)". If upgrading does not stick, something pins it. python -m pip check lists conflicts, and if an installed package requires an older Pillow, pip names it in a warning after the upgrade (… requires pillow<…, but you have pillow … which is incompatible). Common culprits are old pinned requirements.txt files, conda environments that also contain an old Pillow, and Python 3.7 or older, where Pillow 9.1 and later cannot be installed at all (the last release for 3.7 is 9.5, so even there Resampling is available once you upgrade within the 9.x series).

Code that works on old and new Pillow

If you maintain a library or a script that must run everywhere, fall back to the short constants:

import PIL
from PIL import Image

try:                                     # Pillow 9.1 and newer
    LANCZOS = Image.Resampling.LANCZOS
    FLIP_LR = Image.Transpose.FLIP_LEFT_RIGHT
except AttributeError:                   # older Pillow
    LANCZOS = Image.LANCZOS
    FLIP_LR = Image.FLIP_LEFT_RIGHT

img = Image.open("photo.jpg").resize((400, 267), LANCZOS).transpose(FLIP_LR)
print("Pillow", PIL.__version__, "->", img.size)

Pillow 9.0.1 -> (400, 267)

import PIL
from PIL import Image

try:                                     # Pillow 9.1 and newer
    LANCZOS = Image.Resampling.LANCZOS
    FLIP_LR = Image.Transpose.FLIP_LEFT_RIGHT
except AttributeError:                   # older Pillow
    LANCZOS = Image.LANCZOS
    FLIP_LR = Image.FLIP_LEFT_RIGHT

img = Image.open("photo.jpg").resize((400, 267), LANCZOS).transpose(FLIP_LR)
print("Pillow", PIL.__version__, "->", img.size)

Pillow 12.3.0 -> (400, 267)

Simpler still: the short names (Image.LANCZOS, Image.FLIP_LEFT_RIGHT, …) were deprecated in 9.1 but the deprecation was reversed in 9.4, so on current Pillow they are ordinary aliases for the enum members. With warnings turned into errors:

import warnings
from PIL import Image

warnings.simplefilter("error")           # turn any deprecation warning into an error
print(Image.LANCZOS == Image.Resampling.LANCZOS, Image.FLIP_LEFT_RIGHT == Image.Transpose.FLIP_LEFT_RIGHT)

True True

The only names that are truly gone are the ones removed in Pillow 10, such as Image.ANTIALIAS; use Image.LANCZOS for that.

Related

The outputs and images on this page are the real results of running every example with Pillow 12.3.0 on Python 3.13 (Linux) on 2026-10-15. Every example is also re-run automatically on macOS (Darwin 25.6.0, Pillow 12.3.0), Linux (Linux 6.17.0-1022-azure, Pillow 12.3.0), Windows (Windows 2025Server, Pillow 12.3.0); the line under each example shows the result per operating system. The DejaVu Sans font files sit next to each script so font examples behave the same everywhere. Sample photos: NASA/Sam Lott, public domain. Spotted something wrong? Tell us.