Make it so that simply typing 'python -m manim' will embed you in a blank scene to work with

custom_defaults.yml

@@ -25,6 +25,7 @@ tex:
   # executable: "xelatex -no-pdf"
   # template_file: "ctex_template.tex"
   # intermediate_filetype: "xdv"
+universal_import_line: "from manimlib.imports import *"
 style:
   background_color: "#333333"
 quality:

manimlib/config.py

@@ -143,15 +143,17 @@ def get_manim_dir():
 
 
 def get_module(file_name):
-    if file_name == "-":
-        module = types.ModuleType("input_scenes")
-        code = "from manimlib.imports import *\n\n" + sys.stdin.read()
-        try:
-            exec(code, module.__dict__)
-            return module
-        except Exception as e:
-            print(f"Failed to render scene: {str(e)}")
-            sys.exit(2)
+    # if file_name == "-":
+    #     module = types.ModuleType("input_scenes")
+    #     code = "from manimlib.imports import *\n\n" + sys.stdin.read()
+    #     try:
+    #         exec(code, module.__dict__)
+    #         return module
+    #     except Exception as e:
+    #         print(f"Failed to render scene: {str(e)}")
+    #         sys.exit(2)
+    if file_name is None:
+        return None
     else:
         module_name = file_name.replace(os.sep, ".").replace(".py", "")
         spec = importlib.util.spec_from_file_location(module_name, file_name)
@@ -187,7 +189,7 @@ def get_configuration(args):
         "mirror_module_path": custom_defaults["directories"]["mirror_module_path"],
         "output_directory": args.video_dir or custom_defaults["directories"]["output"],
         "file_name": args.file_name,
-        "input_file_path": args.file,
+        "input_file_path": args.file or "",
         "open_file_upon_completion": args.open,
         "show_file_location_upon_completion": args.finder,
         "quiet": args.quiet,

manimlib/extract_scene.py

@@ -1,8 +1,10 @@
 import inspect
 import itertools as it
 import sys
+import logging
 
 from manimlib.scene.scene import Scene
+from manimlib.scene.scene import BlankScene
 import manimlib.constants
 
 
@@ -43,10 +45,6 @@ def prompt_user_for_choice(scene_classes):
 
 
 def get_scenes_to_render(scene_classes, config):
-    if len(scene_classes) == 0:
-        print(manimlib.constants.NO_SCENE_MESSAGE)
-        return []
-
     scene_kwargs = dict([
         (key, config[key])
         for key in [
@@ -61,6 +59,10 @@ def get_scenes_to_render(scene_classes, config):
         ]
     ])
 
+    if len(config["scene_names"]) == 0:
+        # If no module or scenes were passed in, just run the blank scene
+        return [BlankScene(**scene_kwargs)]
+
     if config["write_all"]:
         return [sc(**scene_kwargs) for sc in scene_classes]
 
@@ -74,7 +76,8 @@ def get_scenes_to_render(scene_classes, config):
                 found = True
                 break
         if not found and (scene_name != ""):
-            print(
+            logging.log(
+                logging.ERROR,
                 manimlib.constants.SCENE_NOT_FOUND_MESSAGE.format(
                     scene_name
                 ),
@@ -87,6 +90,9 @@ def get_scenes_to_render(scene_classes, config):
 
 
 def get_scene_classes_from_module(module):
+    if module is None:
+        # If no module was passed in, just run the blank scene
+        return []
     if hasattr(module, "SCENES_IN_ORDER"):
         return module.SCENES_IN_ORDER
     else:

manimlib/scene/scene.py

@@ -13,6 +13,7 @@ from manimlib.animation.animation import Animation
 from manimlib.animation.transform import MoveToTarget
 from manimlib.mobject.mobject import Point
 from manimlib.camera.camera import Camera
+from manimlib.config import get_custom_defaults
 from manimlib.constants import *
 from manimlib.container.container import Container
 from manimlib.mobject.mobject import Mobject
@@ -574,3 +575,9 @@ class Scene(Container):
 
 class EndSceneEarlyException(Exception):
     pass
+
+
+class BlankScene(Scene):
+    def construct(self):
+        exec(get_custom_defaults()["universal_import_line"])
+        self.embed()