{"record":{"id":"47bddb714208da5c","repo":"3b1b/manim","slug":"cannot-call-mobject-for-a-mobject-with-no-point","errorCode":null,"errorMessage":"Cannot call Mobject.{} for a Mobject with no points","messagePattern":"Cannot call Mobject\\.(.+?) for a Mobject with no points","errorType":"exception","errorClass":"Exception","httpStatus":null,"severity":"error","filePath":"manimlib/mobject/mobject.py","lineNumber":2084,"sourceCode":"        self.add_event_listner(EventType.KeyPressEvent, callback)\n\n    def remove_key_press_listner(self, callback):\n        self.remove_event_listner(EventType.KeyPressEvent, callback)\n\n    def add_key_release_listner(self, callback):\n        self.add_event_listner(EventType.KeyReleaseEvent, callback)\n\n    def remove_key_release_listner(self, callback):\n        self.remove_event_listner(EventType.KeyReleaseEvent, callback)\n\n    # Errors\n\n    def throw_error_if_no_points(self):\n        if not self.has_points():\n            message = \"Cannot call Mobject.{} \" +\\\n                      \"for a Mobject with no points\"\n            caller_name = sys._getframe(1).f_code.co_name\n            raise Exception(message.format(caller_name))\n\n\nclass Group(Mobject, Generic[SubmobjectType]):\n    def __init__(self, *mobjects: SubmobjectType | Iterable[SubmobjectType], **kwargs):\n        super().__init__(**kwargs)\n        self._ingest_args(*mobjects)\n\n    def _ingest_args(self, *args: Mobject | Iterable[Mobject]):\n        if len(args) == 0:\n            return\n        if all(isinstance(mob, Mobject) for mob in args):\n            self.add(*args)\n        elif isinstance(args[0], Iterable):\n            self.add(*args[0])\n        else:\n            raise Exception(f\"Invalid argument to Group of type {type(args[0])}\")\n\n    def __add__(self, other: Mobject | Group) -> Self:","sourceCodeStart":2066,"sourceCodeEnd":2102,"githubUrl":"https://github.com/3b1b/manim/blob/dee01804d47b9f94402d71472674710dcac125b8/manimlib/mobject/mobject.py#L2066-L2102","documentation":"Formatted Exception from Mobject.throw_error_if_no_points (manimlib/mobject/mobject.py:2084): 'Cannot call Mobject.{caller} for a Mobject with no points', where {caller} is filled with the immediate caller's function name via sys._getframe(1). Geometry-dependent methods (get_start/get_end in mobject.py:1587-1595, and VMobject point accessors like get_start_anchors/get_end_anchors/get_first_handle/get_points in vectorized_mobject.py:666-726) call it when self.points is empty, because point math on a point-less mobject is meaningless.","triggerScenarios":"Creating a bare Mobject/VMobject (which starts with no points) and calling get_start(), get_end(), get_start_anchors(), apply_function on empty points, or any of the guarded point accessors; calling point methods on a mobject whose points were cleared (e.g. after set_points([]) or before init_points).","commonSituations":"Instantiating VMobject subclasses without initializing points (custom subclass forgetting super().__init__ or init_points); calling geometric helpers on empty containers like VGroup (a Group has no own points) instead of its children; animation code calling get_start/get_end on freshly constructed mobjects before their geometry is generated.","solutions":["Ensure the mobject has points before the call: use built-in shapes (Line, Circle) or implement init_points in custom subclasses","Guard with mob.has_points() before calling point-dependent methods","For containers, call the method on the child mobjects, not the empty container"],"exampleFix":"# before\nmob = VMobject()\nmob.get_start()  # raises: Cannot call Mobject.get_start ...\n\n# after\nmob = VMobject()\nif mob.has_points():\n    start = mob.get_start()\nelse:\n    start = None\n# or construct a real shape first: mob = Line(ORIGIN, RIGHT)","handlingStrategy":"validation","validationCode":"if not mob.has_points():\n    raise ValueError(f\"{mob} has no points; initialize geometry first\")\nstart = mob.get_start()","typeGuard":"def has_geometry(mob) -> bool:\n    return mob.has_points()","tryCatchPattern":"try:\n    p = mob.get_start()\nexcept Exception as e:\n    if \"no points\" in str(e):\n        p = None\n    else:\n        raise","preventionTips":["Call has_points() before point-dependent methods, especially on custom VMobject subclasses","Ensure subclasses run super().__init__ / init_points so geometry exists","Operate on child mobjects, not empty containers like VGroup"],"tags":["manim","mobject","vmobject","points","validation"],"backgroundTag":null,"analyzedSha":"dee01804d47b9f94402d71472674710dcac125b8","analyzedAt":"2026-08-14T19:53:44.241Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}