3b1b/manim · error · Exception

Whoops, looks like you accidentally invoked the method you w

Error message

Whoops, looks like you accidentally invoked the method you want to animate

What it means

ApplyMethod wraps a bound mobject method (e.g. circle.shift) and animates applying it. check_validity_of_input requires inspect.ismethod(method): passing the method's *return value* — i.e. calling it — fails, because the animation needs the callable plus separate args to build the target state.

Source

Thrown at manimlib/animation/transform.py:173

class ApplyMethod(Transform):
    def __init__(self, method: Callable, *args, **kwargs):
        """
        method is a method of Mobject, *args are arguments for
        that method.  Key word arguments should be passed in
        as the last arg, as a dict, since **kwargs is for
        configuration of the transform itself

        Relies on the fact that mobject methods return the mobject
        """
        self.check_validity_of_input(method)
        self.method = method
        self.method_args = args
        super().__init__(method.__self__, **kwargs)

    def check_validity_of_input(self, method: Callable) -> None:
        if not inspect.ismethod(method):
            raise Exception(
                "Whoops, looks like you accidentally invoked "
                "the method you want to animate"
            )
        assert isinstance(method.__self__, Mobject)

    def create_target(self) -> Mobject:
        method = self.method
        # Make sure it's a list so that args.pop() works
        args = list(self.method_args)

        if len(args) > 0 and isinstance(args[-1], dict):
            method_kwargs = args.pop()
        else:
            method_kwargs = {}
        target = method.__self__.copy()
        method.__func__(target, *args, **method_kwargs)
        return target

View on GitHub (pinned to dee01804d4)

Solutions

Pass the method uninvoked with its arguments separately: ApplyMethod(circle.shift, RIGHT)
Prefer the modern syntax: self.play(circle.animate.shift(RIGHT))
For functions that are not mobject methods, use ApplyFunction(function, mobject) instead

Example fix

# before
self.play(ApplyMethod(circle.shift(RIGHT)))
# after
self.play(ApplyMethod(circle.shift, RIGHT))
# or
self.play(circle.animate.shift(RIGHT))

Defensive patterns

Strategy: type-guard

Validate before calling

import inspect
assert inspect.ismethod(circle.shift), "pass the method itself, not its result"

Type guard

import inspect
def is_bound_mobject_method(f) -> bool:
    return inspect.ismethod(f) and isinstance(f.__self__, Mobject)

Prevention

Standardize on mob.animate.method(args) — it removes the call-vs-reference ambiguity entirely
In code review, flag any ApplyMethod(...) whose first argument ends in ')'

When it happens

Trigger: ApplyMethod(circle.shift(RIGHT)) instead of ApplyMethod(circle.shift, RIGHT); passing a free function or lambda instead of a bound method; passing mobject.copy() (returns a Mobject, not a method).

Common situations: Muscle memory from scene.play(circle.shift(RIGHT)); migrating old scripts that mixed direct method calls with ApplyMethod; using .animate and ApplyMethod inconsistently in the same file.

Related errors

AI-assisted analysis of 3b1b/manim@dee01804d4 (2026-08-14). Data as JSON: /api/errors/a5feb485f26a194e. Report an issue: GitHub.