ValueError: class EpochBasedTrainLoop in mmengine/runner/loops.py: class YOLOv5CocoDataset in mmyolo/datasets/yolov5_coco.py: need at least one array to concatenate

[nanpuhaha]

How can I fix it?

Traceback (most recent call last):
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/registry/build_functions.py", line 121, in build_from_cfg
    obj = obj_cls(**args)  # type: ignore
  File "/opt/ml/project/mmyolo/mmyolo/datasets/yolov5_coco.py", line 19, in __init__
    super().__init__(*args, **kwargs)
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmdet/datasets/base_det_dataset.py", line 33, in __init__
    super().__init__(*args, **kwargs)
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/dataset/base_dataset.py", line 247, in __init__
    self.full_init()
  File "/opt/ml/project/mmyolo/mmyolo/datasets/yolov5_coco.py", line 43, in full_init
    self.data_bytes, self.data_address = self._serialize_data()
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/dataset/base_dataset.py", line 764, in _serialize_data
    data_bytes = np.concatenate(data_list)
  File "<__array_function__ internals>", line 180, in concatenate
ValueError: need at least one array to concatenate

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/registry/build_functions.py", line 121, in build_from_cfg
    obj = obj_cls(**args)  # type: ignore
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/runner/loops.py", line 43, in __init__
    super().__init__(runner, dataloader)
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/runner/base_loop.py", line 26, in __init__
    self.dataloader = runner.build_dataloader(
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/runner/runner.py", line 1333, in build_dataloader
    dataset = DATASETS.build(dataset_cfg)
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/registry/registry.py", line 521, in build
    return self.build_func(cfg, *args, **kwargs, registry=self)
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/registry/build_functions.py", line 135, in build_from_cfg
    raise type(e)(
ValueError: class `YOLOv5CocoDataset` in mmyolo/datasets/yolov5_coco.py: need at least one array to concatenate

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "tools/train.py", line 116, in <module>
    main()
  File "tools/train.py", line 112, in main
    runner.train()
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/runner/runner.py", line 1648, in train
    self._train_loop = self.build_train_loop(
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/runner/runner.py", line 1440, in build_train_loop
    loop = LOOPS.build(
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/registry/registry.py", line 521, in build
    return self.build_func(cfg, *args, **kwargs, registry=self)
  File "/opt/conda/envs/open-mmlab/lib/python3.8/site-packages/mmengine/registry/build_functions.py", line 135, in build_from_cfg
    raise type(e)(
ValueError: class `EpochBasedTrainLoop` in mmengine/runner/loops.py: class `YOLOv5CocoDataset` in mmyolo/datasets/yolov5_coco.py: need at least one array to concatenate

[llopen]

Have you solved this problem?

[hhaAndroid]

@nanpuhaha Can you provide details?

[Redreadblack]

metainfo中的classes需要小写，以前是大写，今天刚被@hhaAndroid指导这个问题 ，你可以试试