open-mmlab/mmdetection · error · KeyError

box type {name} has been registered

Error message

box type {name} has been registered

What it means

mmdet keeps a global registry mapping box type names ('hbox', 'rbox', 'qbox') to classes. _register_box raises KeyError on duplicate registration to prevent ambiguous box-type semantics in convert/pack operations; force=True overwrites instead.

Source

Thrown at mmdet/structures/bbox/box_type.py:30

box_types: dict = {}
_box_type_to_name: dict = {}
box_converters: dict = {}


def _register_box(name: str, box_type: Type, force: bool = False) -> None:
    """Register a box type.

    Args:
        name (str): The name of box type.
        box_type (type): Box mode class to be registered.
        force (bool): Whether to override an existing class with the same
            name. Defaults to False.
    """
    assert issubclass(box_type, BaseBoxes)
    name = name.lower()

    if not force and (name in box_types or box_type in _box_type_to_name):
        raise KeyError(f'box type {name} has been registered')
    elif name in box_types:
        _box_type = box_types.pop(name)
        _box_type_to_name.pop(_box_type)
    elif box_type in _box_type_to_name:
        _name = _box_type_to_name.pop(box_type)
        box_types.pop(_name)

    box_types[name] = box_type
    _box_type_to_name[box_type] = name


def register_box(name: str,
                 box_type: Type = None,
                 force: bool = False) -> Union[Type, Callable]:
    """Register a box type.

    A record will be added to ``bbox_types``, whose key is the box type name
    and value is the box type itself. Simultaneously, a reverse dictionary

View on GitHub (pinned to cfd5d3a985)

Solutions

1. Pass force=True when re-registration is intentional (plugins overriding built-in behavior)
2. Use a unique name for custom box types instead of colliding with 'hbox'/'rbox'/'qbox'
3. Restart the kernel / avoid re-importing registration modules in notebooks

Example fix

# before
register_box(MyBoxes, 'hbox')  # KeyError: already registered
# after
register_box(MyBoxes, 'mybox')  # unique name
# or
register_box(MyBoxes, 'hbox', force=True)  # intentional override

from mmdet.structures.bbox import box_types
name = 'mybox'
if name in box_types:
    # already registered, skip or use force
    pass

try:
    register_box(MyBoxes, 'mybox')
except KeyError as e:
    if 'has been registered' in str(e):
        register_box(MyBoxes, 'mybox', force=True)  # if override intended
    else:
        raise

When it happens

Trigger: Calling get_box_type/register machinery twice for the same name — commonly importing a module that re-registers a box type (e.g. re-importing mmdet.structures in a notebook after autoreload, or a third-party plugin registering 'hbox' again without force).

Common situations: Jupyter %autoreload re-executing registration code, plugin packages registering a type name already used by mmdet, or module reloads in test suites.

Related errors

• LoadImageFromFile is not found in the test pipeline
• Visualization needs the "visualizer" termdefined in the conf
• Unsupported input type: {type(single_input)}
• panopticapi is not installed, please install it by: pip inst
• config must be a filename or Config object, but got {type(co

AI-assisted analysis of open-mmlab/mmdetection@cfd5d3a985 (2026-08-27). Data as JSON: /api/errors/f2deb2e62be58011. Report an issue: GitHub.