ImportError: cannot import name 'BaseTrainer' from 'trl.trainer.alignprop_trainer'

[fanconic]

Hi,

I keep running into the same error when trying to run the GRPO tutorial notebook locally:

When import unsloth

from unsloth import FastLanguageModel, PatchFastRL

I get the following error:

File ~/.../unsloth_compiled_cache/UnslothAlignPropTrainer.py:5
      4 from torch.nn import functional as F
...
----> 5 from trl.trainer.alignprop_trainer import (Accelerator, AlignPropConfig, AlignPropTrainer, Any, BaseTrainer, Callable, DDPOStableDiffusionPipeline, MODEL_CARD_TEMPLATE, Optional, ProjectConfiguration, Tuple, defaultdict, logger, os, set_seed, torch, warn, warnings, whoami)
      8 import os
      9 from typing import *

ImportError: cannot import name 'BaseTrainer' from 'trl.trainer.alignprop_trainer' 

I have the following versions:

Python =  3.11.11
torch = 2.5.1+cu124
trl = 0.15.2
diffusers = 0.32.2
unsloth =  2025.3.7
unsloth_zoo = 2025.3.5
vllm = 0.7.3

Do you have any idea how this could be solved?

[danielhanchen]

Could you try reinstalling Unsloth - I just added a fix: pip install --upgrade --force-reinstall --no-deps unsloth unsloth_zoo

[fanconic]

I am unsure what fixed this issue, but reinstalling the newest versions did the trick! Many thanks for your help! Closing the issue