Transformers 4.57.0 declares compatibility with Python>=3.9 but is only compatible with >=3.10
Author: anakin87
Pull request: no
Labels: name: bug

### System Info

- `transformers` version: 4.57.0
- Platform: macOS-15.7-arm64-arm-64bit
- Python version: 3.9.6
- Huggingface_hub version: 0.35.3
- Safetensors version: 0.6.2
- Accelerate version: 1.10.1
- Accelerate config:    not found
- DeepSpeed version: not installed
- PyTorch version (accelerator?): 2.8.0 (NA)
- Tensorflow version (GPU?): not installed (NA)
- Flax version (CPU?/GPU?/TPU?): not installed (NA)
- Jax version: not installed
- JaxLib version: not installed
- Using distributed or parallel set-up in script?: <fill in>

### Who can help?

_No response_

### Information

- [x] The official example scripts
- [ ] My own modified scripts

### Tasks

- [ ] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...)
- [ ] My own task or dataset (give details below)

### Reproduction

1. Use Python 3.9 and do `pip install -U "transformers[torch]"`
2. `from transformers import  Trainer`

Error:
```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<frozen importlib._bootstrap>", line 1055, in _handle_fromlist
  File "/omitted/.venv/lib/python3.9/site-packages/transformers/utils/import_utils.py", line 2317, in __getattr__
    module = self._get_module(self._class_to_module[name])
  File "/omitted/.venv/lib/python3.9/site-packages/transformers/utils/import_utils.py", line 2347, in _get_module
    raise e
  File "/omitted/.venv/lib/python3.9/site-packages/transformers/utils/import_utils.py", line 2345, in _get_module
    return importlib.import_module("." + module_name, self.__name__)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "/omitted/.venv/lib/python3.9/site-packages/transformers/trainer.py", line 311, in <module>
    class Trainer:
  File "/omitted/.venv/lib/python3.9/site-packages/transformers/trainer.py", line 5593, in Trainer
    def _get_num_items_in_batch(self, batch_samples: list, device: torch.device) -> int | None:
TypeError: unsupported operand type(s) for |: 'type' and 'NoneType'
```

### Expected behavior

Currently, Transformers [requires Python>=3.9](https://pypi.org/project/transformers/4.57.0/) but only works with Python>=3.10

I see two possible solutions:
- Python 3.9 is reaching its End Of Life this month, so I think it can be dropped
- Modify the implementations to remove syntaxes that are only supported in >=3.10 (such as `|` instead of `Union`)

Comments:
Sorry for that ! The issue should be fixed here https://github.com/huggingface/transformers/pull/41359 and we will release a patch in the following days. Note that for the next release v5, we will drop support for py3.9

@SunMarc feel free to close this if you think it's solved. Thanks!

I will close it when the patch release is out ! The main branch is not compatible with py3.9

Hi, It doesn't work for me with python 3.10 and 3.11 either. Could you please double check @anakin87 ? I have the same system env. 

A patch was released for v4.57 to fix py3.9 compatibility https://github.com/huggingface/transformers/releases/tag/v4.57.1