update Singleton

Author: rambasnet

notebooks/PythonObjects-Singleton.ipynb

@@ -1013,7 +1013,6 @@
     "- since python doesn't have a private access specifier, we've to be a little creative\n",
     "- can use `__new__()` method and class variable to ensure that only one instance is created\n",
     "- also called anti-pattern because there is only one instance of the class\n",
-    "- use `__new__()` method to create a new instance of the class\n",
     "- `__new__()` is a class method that is called before the `__init__()` instance method\n",
     "- use `cls` parameter to check if the instance is already created\n",
     "- return the instance if it's already created\n",
@@ -1031,25 +1030,28 @@
    "source": [
     "from __future__ import annotations\n",
     "\n",
+    "\n",
     "class MySingletonClass:\n",
-    "    _instance: \"MyClass\" | None = None\n",
+    "    _instance: \"MySingletonClass\" | None = None\n",
     "\n",
     "    # singleton pattern\n",
     "    def __new__(cls, *args, **kwargs):\n",
     "        # we don't care about (a, b) so use args and kwargs within __new__\n",
-    "        # not providing them will create syntax error because __init__ is defined with two arguments \n",
+    "        # not providing them will create syntax error because __init__ is defined with two arguments\n",
     "        if not cls._instance:\n",
     "            cls._instance = super().__new__(cls, *args, **kwargs)\n",
     "        return cls._instance\n",
     "\n",
-    "    def __init__(self, a, b):\n",
+    "    def __init__(self, a: int, b: int) -> None:\n",
     "        self.a = a\n",
     "        self.b = b\n",
     "\n",
-    "    def __str__(self):\n",
+    "    def __str__(self) -> str:\n",
     "        return f'{self.a}, {self.b}'\n",
-    "    \n",
-    "    def __eq__(self, other):\n",
+    "\n",
+    "    def __eq__(self, other: object) -> bool:\n",
+    "        if not isinstance(other, MySingletonClass):\n",
+    "            return NotImplemented\n",
     "        return self.a == other.a and self.b == other.b"
    ]
   },