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Merge branch 'issue/7'
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‎notebooks/PythonObjects.ipynb

Lines changed: 170 additions & 14 deletions
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@@ -778,7 +778,7 @@
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},
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{
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"cell_type": "code",
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"execution_count": 86,
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"execution_count": null,
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"id": "032da8ae",
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"metadata": {},
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"outputs": [],
@@ -835,7 +835,7 @@
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" l_name = property(fget=_get_last_name, \n",
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" fset=_set_last_name,\n",
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" fdel=_del_last_name,\n",
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" doc=\"Last name property.\"\n",
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" doc=\"Last Name property.\"\n",
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" )"
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]
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},
@@ -1170,15 +1170,19 @@
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"execution_count": 7,
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"id": "e4a91bd1",
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"metadata": {},
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"outputs": [],
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"source": [
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"class MyClass:\n",
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" class_var = 10\n",
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"\n",
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" def __init__(self, a=5, b=10):\n",
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" self.a = a\n",
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" self.b = b\n",
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" \n",
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" def method(self, a, b):\n",
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" def set_method(self, a, b):\n",
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" self.a = a\n",
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" self.b = b\n",
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" return 'instance method called', self, self.__add()\n",
@@ -1197,29 +1201,29 @@
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"execution_count": 9,
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"id": "132ecac5",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"('instance method called', <__main__.MyClass at 0x7fe1e021e710>, 15)"
1211+
"('instance method called', <__main__.MyClass at 0x78cb4862cd40>, 15)"
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]
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},
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"execution_count": 2,
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"execution_count": 9,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"instance = MyClass()\n",
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"instance.method(2, 3)"
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"instance.set_method(2, 3)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 104,
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"execution_count": 12,
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"id": "aeca739a",
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"metadata": {},
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"outputs": [
@@ -1229,7 +1233,7 @@
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"('class method called', __main__.MyClass, 18)"
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]
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},
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"execution_count": 104,
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"execution_count": 12,
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"metadata": {},
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"output_type": "execute_result"
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}
@@ -1241,7 +1245,7 @@
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},
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{
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"cell_type": "code",
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"execution_count": 105,
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"execution_count": 13,
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"id": "961ace48",
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"metadata": {},
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"outputs": [
@@ -1251,7 +1255,7 @@
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"('static method called', 18)"
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]
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},
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"execution_count": 105,
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"execution_count": 13,
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"metadata": {},
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"output_type": "execute_result"
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}
@@ -1261,6 +1265,158 @@
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"MyClass.staticmethod(3, 5)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 14,
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"id": "1968f5cf",
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"metadata": {},
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"outputs": [],
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"source": [
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"# multiple instances of MyClass is allowed and expected\n",
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"instance1 = MyClass()\n",
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"instance2 = MyClass()"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 15,
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"id": "de470975",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"False"
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]
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},
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"execution_count": 15,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"# those instances are in fact different objects\n",
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"instance1 is instance2"
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]
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},
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{
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"cell_type": "markdown",
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"id": "1f17389d",
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"metadata": {},
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"source": [
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"## Singleton Pattern\n",
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"\n",
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"- also called anti-pattern because there is only one instance of the class\n",
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"- use `__new__()` method to create a new instance of the class\n",
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"- use `cls` parameter to check if the instance is already created\n",
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"- return the instance if it's already created\n",
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"- otherwise, create a new instance and return it"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 41,
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"id": "4e8f863a",
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"metadata": {},
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"outputs": [],
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"source": [
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"from __future__ import annotations\n",
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"\n",
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"class MySingletonClass:\n",
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" _instance: \"MyClass\" | None = None\n",
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"\n",
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" # singleton pattern\n",
1329+
" def __new__(cls, *args, **kwargs):\n",
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" # we don't care about args and kwargs within __new__\n",
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" # not providing them will create syntax error because __init__ is defined with two arguments \n",
1332+
" if not cls._instance:\n",
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" cls._instance = super().__new__(cls)\n",
1334+
" return cls._instance\n",
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"\n",
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" def __init__(self, a, b):\n",
1337+
" self.a = a\n",
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" self.b = b\n",
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"\n",
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" def __str__(self):\n",
1341+
" return f'{self.a}, {self.b}'\n",
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" \n",
1343+
" def __eq__(self, other):\n",
1344+
" return self.a == other.a and self.b == other.b"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 42,
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"id": "a764ca44",
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"metadata": {},
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"outputs": [],
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"source": [
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"obj1 = MySingletonClass(2, 3)\n",
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"obj2 = MySingletonClass(3, 4)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 43,
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"id": "b9b63da3",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"True"
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]
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},
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"execution_count": 43,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"obj1 is obj2"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 44,
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"id": "b302bf1f",
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"3, 4\n",
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"3, 4\n"
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]
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}
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],
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"source": [
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"print(obj1)\n",
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"print(obj2)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 45,
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"id": "ad9b3855",
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"True"
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]
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},
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"execution_count": 45,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"obj1 == obj2"
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]
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},
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{
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"cell_type": "markdown",
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"id": "bb3b269c",
@@ -1330,7 +1486,7 @@
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],
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"metadata": {
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"kernelspec": {
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"display_name": "oop",
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
@@ -1344,7 +1500,7 @@
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.10.9"
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"version": "3.12.1"
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}
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},
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"nbformat": 4,

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