Add type annotations to `mobject.py` #4388

henrikmidtiby · 2025-08-10T19:00:58Z

Overview: What does this pull request change?

This PR add type annotations to mobject.py.

Reviewer Checklist

The PR title is descriptive enough for the changelog, and the PR is labeled correctly
If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
If applicable: newly added functions and classes are tested

henrikmidtiby · 2025-08-10T20:00:10Z

manim/mobject/geometry/line.py

+            # error: Argument "tip" to "add_tip" of "TipableVMobject" has incompatible type "VMobject"; expected "ArrowTip | None"  [arg-type]
            self.add_tip(tip=old_tips[0])
        if has_start_tip:
+            # error: Argument "tip" to "add_tip" of "TipableVMobject" has incompatible type "VMobject"; expected "ArrowTip | None"  [arg-type]
            self.add_tip(tip=old_tips[1], at_start=True)


These issues can be handled by typing.cast, but I don't think that is the best way to deal with them.

henrikmidtiby · 2025-08-10T20:02:48Z

manim/mobject/types/vectorized_mobject.py

+    def __getitem__(self, key: int) -> VMobject:
+        return self.submobjects[key]
+


This method is used to define the return type when indexing into a VGroup. If the super class was used, this would return a Mobject, but in a VGroup it should be a VMobject.

henrikmidtiby · 2025-08-10T20:05:06Z

manim/scene/vector_space_scene.py

+        temp = self.get_basis_vectors()
+        i_hat = temp.submobjects[0]
+        j_hat = temp.submobjects[1]


Apparently the trick for defining the type of elements in a VGroup to be VMobject's does not work here. Which is the reason for this workaround.

That's strange, but OK...

henrikmidtiby · 2025-08-10T20:06:02Z

manim/scene/vector_space_scene.py

+        temp = array.get_entries()
+        x_coord = temp.submobjects[0]
+        y_coord = temp.submobjects[1]


Apparently the trick for defining the type of elements in a VGroup to be VMobject's does not work here. Which is the reason for this workaround.

henrikmidtiby · 2025-08-10T20:06:45Z

manim/utils/color/core.py

    reference_colors: Sequence[ParsableManimColor],
    length_of_output: int,
-) -> list[ManimColor] | ManimColor:
+) -> list[ManimColor]:


Same change as in PR #4380

henrikmidtiby · 2025-08-10T20:07:00Z

manim/utils/color/core.py

    """
    if length_of_output == 0:
-        return ManimColor(reference_colors[0])
+        return [ManimColor(reference_colors[0])]


Same change as in PR #4380.

henrikmidtiby · 2025-08-10T20:11:09Z

manim/mobject/mobject.py

+    animation_overrides: dict[
+        type[Animation],
+        FunctionOverride,
+    ] = {}


By specifying the type of animation_overrides here, a lot of type errors like "type[Mobject]" has no attribute "animation_overrides" are removed.

manim/mobject/mobject.py

henrikmidtiby · 2025-08-11T12:24:35Z

One of the main contributions in this PR is that when accessing elements in a VGroup, the type of these elements are now recognized as VMobjects.

This is achieved by adding/modifying these methods including type annotations to the VMobject class.

def __iter__(self) -> Iterator[VMobject]:
    return iter(self.split())
def split(self) -> list[VMobject]:
    result: list[VMobject] = [self] if len(self.points) > 0 else []
    return result + self.submobjects

And these to the VGroup class.

def __getitem__(self, key: int) -> VMobject:
    return self.submobjects[key]

…2282

… code for the remaning 10 errors

…in elements during runtime and not only during type checking

for more information, see https://pre-commit.ci

chopan050

Thanks for the huge contribution!

I left some suggestions:

manim/animation/indication.py

manim/camera/moving_camera.py

manim/mobject/graphing/probability.py

chopan050 · 2025-11-26T02:59:54Z

manim/mobject/text/code_mobject.py

-                line[start:end].set_color(color)
+                if end == start:
+                    continue
+                for single_line in line[start:end]:
+                    single_line.set_color(color)


Checking both the original and the new code with MyPy locally, it shows no difference _{(in both cases, there is an error because Mobject.set_color() does not accept None as an argument)}, so I don't really understand the reason for this change...

Strange, on my computer I get the following error with the original code when I run the pytest testsuite.

for line, color_range in zip(self.code_lines, color_ranges): for start, end, color in color_range: > line[start:end].set_color(color) E AttributeError: 'list' object has no attribute 'set_color'

manim/mobject/text/tex_mobject.py

manim/mobject/mobject.py

chopan050 · 2025-12-04T14:08:33Z

manim/mobject/mobject.py

+        # error: "Callable[..., Animation]" has no attribute "_override_animate"  [attr-defined]
+        temp_method._override_animate = animation_method


Typing method so that it has a dynamic attribute _override_animate is difficult.

I propose the following alternative, maybe for another PR: create an _AnimationBuilder class dictionary _AnimationBuilder.animate_override_map: dict[int, types.MethodType] which maps method IDs to their .animate overrides. Thus, this line could be replaced with

_AnimationBuilder.animate_override_map[id(method)] = animation_method

Inside _AnimationBuilder.__getattr__(), instead of doing

has_overriden_animation = hasattr(method, "_override_animate")

we could do

method_override = self.animate_override_map.get(id(method), None)

and then use it inside the internal function update_target().

In the meantime, let's just type ignore this one:

Suggested change

# error: "Callable[..., Animation]" has no attribute "_override_animate" [attr-defined]

temp_method._override_animate = animation_method

method._override_animate = animation_method # type: ignore[attr-defined]

Lets take this in a separate PR.

chopan050 · 2025-12-04T18:38:21Z

manim/scene/vector_space_scene.py

+        temp = self.get_basis_vectors()
+        i_hat = temp.submobjects[0]
+        j_hat = temp.submobjects[1]


That's strange, but OK...

manim/scene/vector_space_scene.py

chopan050

Thanks for the huge contribution!

I left some suggestions. In particular, a raise ValueError(...) inside Mobject.arrange_in_grid() is causing an error while building the docs, so that one requires more attention.

…hinting

…future cleanup task

Co-authored-by: Francisco Manríquez Novoa <49853152+chopan050@users.noreply.github.com>

for more information, see https://pre-commit.ci

manim/camera/moving_camera.py

+        margin: float,
+        only_mobjects_in_frame: bool,
+        animate: Literal[False],
+    ) -> Mobject: ...


manim/camera/moving_camera.py

+        margin: float,
+        only_mobjects_in_frame: bool,
+        animate: Literal[True],
+    ) -> _AnimationBuilder: ...


henrikmidtiby · 2025-12-04T22:03:15Z

@chopan050 Thanks for all the comments, even the minor nitpicks! I feel they help me improving the PR.
I will get back to resolving the remaining suggestions in the coming days.

henrikmidtiby · 2025-12-05T08:34:11Z

The raise ValueError is now handled.
Then I discovered a new issue, with the following example

from manim import *

# Scene derived from the example given in the documentation
class TableExamples(Scene):
    def construct(self):
        t2 = MathTable(
            [["+", 0, 5, 10],
            [0, 0, 5, 10],
            [2, 2, 7, 12],
            [4, 4, 9, 14]],
            include_outer_lines=True)

        for line in t2.get_horizontal_lines()[:3]:
            line.set_color(BLUE)

        t2.get_vertical_lines().set_color(BLUE)
        t2.get_vertical_lines()[0].set_color(BLUE)

        # AttributeError: 'list' object has no attribute 'set_color'
        t2.get_vertical_lines()[:3].set_color(BLUE)

I have attempted to solve the issue through implementing a __getitem__ method in the VGroup class. But apparently it does not work... Here is the used implementation.

    def __getitem__(self, item: int) -> Self:
        return self.submobjects[item]

# Conflicts: # manim/mobject/matrix.py # manim/mobject/mobject.py # manim/mobject/types/vectorized_mobject.py

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henrikmidtiby commented Aug 10, 2025

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manim/mobject/mobject.py Fixed Show fixed Hide fixed

henrikmidtiby changed the title ~~Typing mobject.py~~ Add type annotations to mobject.py Aug 13, 2025

henrikmidtiby mentioned this pull request Aug 13, 2025

Typing progress tracker #3375

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RBerga06 mentioned this pull request Aug 15, 2025

Add type annotations to opengl_mobject.py #4398

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henrikmidtiby marked this pull request as ready for review August 21, 2025 21:31

henrikmidtiby added the typehints For adding/discussing typehints label Dec 1, 2025

henrikmidtiby added 14 commits December 2, 2025 15:43

Add type annotations to mobject.py

953c07d

More work on type annotations for mobject.py

8c35540

...

be6d3ca

Almost handled all mypy errors

7ce05ff

Add the mypy error messages to the lines that trigger them

4629173

Use typing.cast to avoid some mypy errors, as suggested by JasonGrace…

e80f22c

…2282

Used the ruff linter

e9e797e

Fixed one typing issue and added the error descriptions to the source…

8ec81a2

… code for the remaning 10 errors

Set the type of the elements in a VGroup to VMobject

3b39095

Use typing.cast to handle some specific cases.

0db274f

Code cleaning

9f45342

Updates

4f21679

When started to use typing.cast it is needed to import / define certa…

43a8b47

…in elements during runtime and not only during type checking

Fix bug introduced with the type annotations.

0ec7b7b

[pre-commit.ci] auto fixes from pre-commit.com hooks

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henrikmidtiby force-pushed the TypingMobject branch from 15d4832 to f14e5c3 Compare December 2, 2025 14:53

chopan050 requested changes Dec 4, 2025

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henrikmidtiby and others added 8 commits December 4, 2025 21:43

Remove comment that is no longer relevant

1bc6893

Overload the auto_zoom method in MovingCamera to provide better type …

bc5ab06

…hinting

Codecleanup

0ed7dcc

Code cleanup

edc8b8f

Renamed lines_alignment to lines_alignments and added a TODO about a …

47643dc

…future cleanup task

More code cleanup

470c8da

Update manim/mobject/matrix.py

14c4c45

Co-authored-by: Francisco Manríquez Novoa <49853152+chopan050@users.noreply.github.com>

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henrikmidtiby added 3 commits December 4, 2025 22:33

Addressing multiple comments from Chopan50

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Implementing more suggestions from Chopan50

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More suggestions by Chopan50

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henrikmidtiby added 6 commits December 5, 2025 08:22

...

2e85869

More renaming and code cleanup, as suggested by Chopan50

eafb1ac

Restructure code

13c8c7d

anim_args

9371cdd

Update typing in vector_space_scene

81014c9

Implemented a number of suggestions from chopan50

8aa0b72

henrikmidtiby added 5 commits January 12, 2026 09:40

Merge branch 'main' into TypingMobject

694d62d

Make a list of faces with the type list[ThreeDVMobject]

4d6214a

Ensure to return a VGroup if slicing is used.

4ffc91f

Revert back to the original code in text_mobject.py

5894b7d

Merge branch 'main' into TypingMobject

b5bafdc

# Conflicts: # manim/mobject/matrix.py # manim/mobject/mobject.py # manim/mobject/types/vectorized_mobject.py

		def __getitem__(self, key: int) -> VMobject:
		return self.submobjects[key]

		# error: "Callable[..., Animation]" has no attribute "_override_animate" [attr-defined]
		temp_method._override_animate = animation_method

	# error: "Callable[..., Animation]" has no attribute "_override_animate" [attr-defined]
	temp_method._override_animate = animation_method
	method._override_animate = animation_method # type: ignore[attr-defined]

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Add type annotations to `mobject.py` #4388

Add type annotations to `mobject.py` #4388

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