169 lines
4.6 KiB
Plaintext
169 lines
4.6 KiB
Plaintext
{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Pure Python Metaclass"
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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": 1,
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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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"Initializing singleton: 21aac41a-ee95-40c0-88f1-f55eaf81ac60\n",
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"MySingleton(uuid=UUID('21aac41a-ee95-40c0-88f1-f55eaf81ac60'))\n",
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"MySingleton(uuid=UUID('21aac41a-ee95-40c0-88f1-f55eaf81ac60'))\n",
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"MySingleton(uuid=UUID('21aac41a-ee95-40c0-88f1-f55eaf81ac60'))\n",
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"MySingleton(uuid=UUID('21aac41a-ee95-40c0-88f1-f55eaf81ac60'))\n",
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"MySingleton(uuid=UUID('21aac41a-ee95-40c0-88f1-f55eaf81ac60'))\n"
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]
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}
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],
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"source": [
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"from dataclasses import dataclass, field\n",
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"from uuid import UUID, uuid4\n",
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"\n",
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"\n",
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"# Metaclass definition\n",
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"class Singleton(type):\n",
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" _instances = {}\n",
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"\n",
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" def __call__(cls, *args, **kwargs):\n",
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" if cls not in cls._instances:\n",
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" cls._instances[cls] = super().__call__(*args, **kwargs)\n",
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" return cls._instances[cls]\n",
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"\n",
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"\n",
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"# gives an example of inheritance\n",
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"@dataclass\n",
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"class ParentClass:\n",
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" uuid: UUID = field(init=False, default_factory=uuid4)\n",
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"\n",
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"\n",
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"# Main singleton class\n",
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"@dataclass\n",
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"class MySingleton(ParentClass, metaclass=Singleton):\n",
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" def __post_init__(self):\n",
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" print(f'Initializing singleton: {self.uuid}')\n",
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"\n",
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"\n",
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"# Initialize the singleton\n",
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"MySingleton()\n",
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"\n",
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"# \"Initialize\" a few more times\n",
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"for _ in range(5):\n",
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" print(MySingleton())"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Pydantic Metaclass"
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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": 2,
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"metadata": {},
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"outputs": [],
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"source": [
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"from typing import Any, Optional, Self\n",
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"\n",
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"from pydantic import BaseModel, Field\n",
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"from pydantic._internal._model_construction import ModelMetaclass\n",
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"\n",
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"\n",
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"class PydanticSingleton(ModelMetaclass):\n",
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" _instances = {}\n",
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"\n",
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" def __call__(cls, *args, **kwargs):\n",
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" if model := cls._instances.get(cls):\n",
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" model_dict = model.model_dump()\n",
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" model_dict.update(kwargs)\n",
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" model = model.model_validate(model_dict)\n",
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" cls._instances[cls] = model\n",
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" else:\n",
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" cls._instances[cls] = super(PydanticSingleton, cls).__call__(*args, **kwargs)\n",
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"\n",
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" return cls._instances[cls]\n",
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"\n",
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"\n",
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"class MyPydanticSingleton(BaseModel, metaclass=PydanticSingleton):\n",
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" id: UUID = Field(default_factory=uuid4)\n",
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" required_field: str\n",
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" foo: Optional[str] = None"
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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": 3,
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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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"id=UUID('9965c864-20b7-4809-b73a-c16c352fea20') required_field='Iteration 0' foo=None\n",
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"id=UUID('9965c864-20b7-4809-b73a-c16c352fea20') required_field='Iteration 1' foo=None\n",
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"id=UUID('9965c864-20b7-4809-b73a-c16c352fea20') required_field='Iteration 2' foo=None\n",
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"id=UUID('9965c864-20b7-4809-b73a-c16c352fea20') required_field='Iteration 3' foo=None\n",
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"id=UUID('9965c864-20b7-4809-b73a-c16c352fea20') required_field='Iteration 4' foo=None\n"
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]
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}
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],
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"source": [
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"s = [MyPydanticSingleton(required_field=f'Iteration {i}') for i in range(5)]\n",
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"print('\\n'.join(map(str, s)))"
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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": 4,
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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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"MyPydanticSingleton(id=UUID('9965c864-20b7-4809-b73a-c16c352fea20'), required_field='Iteration 4', foo='bar')"
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]
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},
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"execution_count": 4,
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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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"MyPydanticSingleton(foo='bar')"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "appdaemon",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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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": "3.11.8"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 2
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}
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