Add __all__

book/pythontricks/Chapter.ipynb

@@ -1099,6 +1099,49 @@
     "# Better\n",
     "from module import Class1, Class2, Class3"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Control What Gets Imported"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "How to control what gets imported when you use `from module import *` in Python?\n",
+    "\n",
+    "`__all__` lets you specify which symbols should be imported when you run `from module import *`.\n",
+    "\n",
+    "By defining `__all__` in your module, you can explicitly control what gets exposed."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# mymodule.py\n",
+    "__all__ = ['my_function', 'MyClass']\n",
+    "\n",
+    "def my_function():\n",
+    "    pass\n",
+    "\n",
+    "class MyClass:\n",
+    "    pass\n",
+    "\n",
+    "def internal_helper():\n",
+    "    pass\n",
+    "\n",
+    "# main.py\n",
+    "from mymodule import *\n",
+    "\n",
+    "my_function()\n",
+    "internal_helper() # Error"
+   ]
   }
  ],
  "metadata": {