help

src/textual/cli/cli.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from typing import cast, TYPE_CHECKING
 
 from importlib_metadata import version
 
@@ -28,6 +28,18 @@ class AppFail(Exception):
 
 
 def import_app(import_name: str) -> App:
+    """Import an app from it's import name.
+
+    Args:
+        import_name (str): A name to import, such as `foo.bar`
+
+    Raises:
+        AppFail: If the app could not be found for any reason.
+
+    Returns:
+        App: A Textual application
+    """
+
     import inspect
     import importlib
     import sys
@@ -39,10 +51,26 @@ def import_app(import_name: str) -> App:
     lib, _colon, name = import_name.partition(":")
     name = name or "app"
 
+    if lib.endswith(".py"):
+        # We're assuming the user wants to load a .py file
+        try:
+            with open(lib) as python_file:
+                py_code = python_file.read()
+        except Exception as error:
+            raise AppFail(str(error))
+
+        global_vars: dict[str, object] = {}
+        exec(py_code, global_vars)
+
+        try:
+            app = global_vars[name]
+        except KeyError:
+            raise AppFail(f"App {name!r} not found in {lib!r}")
+    else:
+        # Assuming the user wants to import the file
         try:
             module = importlib.import_module(lib)
         except ImportError as error:
-        raise
             raise AppFail(str(error))
 
         try:
@@ -53,14 +81,30 @@ def import_app(import_name: str) -> App:
     if inspect.isclass(app) and issubclass(app, App):
         app = App()
 
-    return app
+    return cast(App, app)
 
 
 @run.command("run")
-@click.argument("import_name", metavar="IMPORT")
+@click.argument("import_name", metavar="FILE or FILE:APP")
 @click.option("--dev", "dev", help="Enable development mode", is_flag=True)
 def run_app(import_name: str, dev: bool) -> None:
-    """Run a Textual app."""
+    """Run a Textual app.
+
+    The code to run may be given as a path (ending with .py) or as a Python
+    import, which will load the code and run an app called "app". You may optionally
+    add a colon plus the class or class instance you want to run.
+
+    Here are some examples:
+
+    textual run foo.py
+
+    textual run foo.py:MyApp
+
+    textual run module.foo
+
+    textual run module.foo:MyApp
+
+    """
 
     import os
     import sys