3b1b/manim · error

Invalid scene number

Error message

Invalid scene number

What it means

When multiple scenes exist and none is named on the command line, manim prints a numbered menu and reads a comma-separated selection. A token that is numeric indexes scene_classes[int(s) - 1]; an out-of-range number raises IndexError, which is caught, logged as 'Invalid scene number', and exits with status 2.

Source

Thrown at manimlib/extract_scene.py:54

        return False
    return True


def prompt_user_for_choice(scene_classes):
    name_to_class = {}
    max_digits = len(str(len(scene_classes)))
    for idx, scene_class in enumerate(scene_classes, start=1):
        name = scene_class.__name__
        print(f"{str(idx).zfill(max_digits)}: {name}")
        name_to_class[name] = scene_class
    try:
        user_input = input("\nSelect which scene to render (by name or number): ")
        return [
            name_to_class[split_str] if not split_str.isnumeric() else scene_classes[int(split_str) - 1]
            for split_str in user_input.replace(" ", "").split(",")
        ]
    except IndexError:
        log.error("Invalid scene number")
        sys.exit(2)
    except KeyError:
        log.error("Invalid scene name")
        sys.exit(2)
    except EOFError:
        sys.exit(1)


def compute_total_frames(scene_class, scene_config):
    """
    When a scene is being written to file, a copy of the scene is run with
    skip_animations set to true so as to count how many frames it will require.
    This allows for a total progress bar on rendering, and also allows runtime
    errors to be exposed preemptively for long running scenes.
    """
    pre_config = copy.deepcopy(scene_config)
    pre_config["file_writer_config"]["write_to_movie"] = False
    pre_config["file_writer_config"]["save_last_frame"] = False

View on GitHub (pinned to dee01804d4)

Solutions

1. Pick a number between 1 and the count shown in the menu
2. Bypass the menu entirely by naming the scene: manim file.py MyScene
3. In scripts, pass scene names via CLI args instead of relying on interactive stdin

Example fix

# before
$ manim file.py   # menu shows 1: A, 2: B
> 3
# after
$ manim file.py B

choice = input("Scene number: ")
n = int(choice)
assert 1 <= n <= len(scene_classes), f"pick 1..{len(scene_classes)}"

def is_valid_scene_number(s: str, count: int) -> bool:
    return s.isnumeric() and 1 <= int(s) <= count

When it happens

Trigger: Entering '5' or '0' when only 3 scenes are listed; entering '2,7' where 7 exceeds the count; leading zeros are fine but a number past the end is not.

Common situations: Miscounting the printed menu; piping a stale selection into stdin from a script that assumed an older scene list; typing the line number of the file instead of the menu number.

Related errors

• Invalid scene name
• No scene named {name} found
• Please use a valid color
• No 'class' found above {line_number}!

AI-assisted analysis of 3b1b/manim@dee01804d4 (2026-08-14). Data as JSON: /api/errors/dc6d89325ff0af5e. Report an issue: GitHub.