{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "18c0435e-cd1b-4d1b-a9c5-7ccc02d5da72",
   "metadata": {},
   "source": [
    "# Creating classes in Python\n",
    "\n",
    "# Attribute vs property and class containers\n",
    "\n",
    "Germain Salvato Vallverdu\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e7d7bdd9-4f1a-4f2d-89f2-9e4567c508aa",
   "metadata": {},
   "source": [
    "## Without property"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "4f856eef-d27d-4919-9290-e9c654226f7f",
   "metadata": {},
   "outputs": [],
   "source": [
    "class Leaf:\n",
    "    \"\"\" This class represents a leaf's tree \"\"\"\n",
    "    \n",
    "    def __init__(self, width: float, length: float, color: str = \"green\"):\n",
    "        \n",
    "        self.width = width\n",
    "        self.length = length\n",
    "        self.color = color\n",
    "        \n",
    "    def get_area(self):\n",
    "        return self.width * self.length"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "67df53fd-d7d7-44aa-b2ea-037332ac3fb5",
   "metadata": {},
   "outputs": [],
   "source": [
    "l = Leaf(4, 12)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "9e405032-9c6d-440c-9341-b31d1f787442",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<__main__.Leaf at 0x7f7e3a37ae80>"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "37f6d5a4-da17-4926-a251-aec2438dbadf",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(4, 12, 'green')"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.width, l.length, l.color"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "fcfa4c9c-8559-44ab-913c-134df4561e8c",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "48"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.get_area()"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "0a1cecb1-c2a9-4405-ae99-5c297f72a067",
   "metadata": {},
   "source": [
    "By default there is no control on attribute. You can thus change their value."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "7491307e-d3d2-4c7b-aeda-eaaef439268c",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "-60"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# not any control\n",
    "l.width = -5\n",
    "l.get_area()"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "3416ef32-ffed-43b2-bdeb-199bd5110b8c",
   "metadata": {},
   "source": [
    "All python object are fully dynamic. Attribute are thus created on the fly even\n",
    "on instances."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "id": "c47dd7fc-30f9-40bc-a033-5efe26b3182d",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'width': -5, 'length': 12, 'color': 'green', 'weight': 18}"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# really no control\n",
    "l.weight = 18\n",
    "vars(l)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ef4e0ae1-c9e8-4b37-8695-0563557ab891",
   "metadata": {},
   "source": [
    "## Define properties"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "id": "fe57739b-6203-4689-b098-7b8350a566df",
   "metadata": {},
   "outputs": [],
   "source": [
    "class Leaf:\n",
    "    \"\"\" This class represents a leaf's tree \"\"\"\n",
    "    \n",
    "    def __init__(self, width: float, length: float, color: str = \"green\"):\n",
    "        \n",
    "        self.width = width\n",
    "        self.length = length\n",
    "        self.color = color\n",
    "        \n",
    "        # for the sake of efficiency it is better to compute it one times in\n",
    "        # the init. If you don't, you will compute it each time you use the\n",
    "        # property\n",
    "        self._area = self.width * self.length\n",
    "   \n",
    "    @property\n",
    "    def area(self):\n",
    "        \"\"\" Area of the leaf \"\"\"\n",
    "        return self._area"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "id": "aebb08ab-aace-4795-8990-082119b97610",
   "metadata": {},
   "outputs": [],
   "source": [
    "l = Leaf(4, 12)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "34639bb0-ea44-4b21-843b-c2137a8871ad",
   "metadata": {},
   "source": [
    "`area` is now a property and no more a function/method."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "id": "9a7a9215-ca7c-4fcd-ba9c-5b8dad0ba819",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "48"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.area"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "d4f045d5-f9ed-4d01-b1ad-c18dec6ad81a",
   "metadata": {},
   "source": [
    "You are still able to set the `width` or other attributres but not the `area` which is a property.\n",
    "\n",
    "This leads to strange or erroneous behavior."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "id": "dcb5dddd-17a0-458b-827a-bfdef9030348",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "48"
      ]
     },
     "execution_count": 23,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.width = -5\n",
    "l.area"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "id": "faa48669-b690-4ff2-a76a-76c5e672f1e9",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "can't set attribute\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    l.area = -5\n",
    "except AttributeError as error:\n",
    "    print(\"#ERROR#\", error)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ad37a9d5-a3a2-4fcf-be56-48e1847fc86e",
   "metadata": {},
   "source": [
    "## Define more properties\n",
    "\n",
    "We assume the following:\n",
    "\n",
    "* area is a property computed from init data\n",
    "* width and length cannot be changed after the instance is created"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "id": "76b9cbbb-abf2-48bc-9f3a-77ff0176c8d2",
   "metadata": {},
   "outputs": [],
   "source": [
    "class Leaf:\n",
    "    \"\"\" This class represents a leaf's tree \"\"\"\n",
    "    \n",
    "    def __init__(self, width: float, length: float, color: str = \"green\"):\n",
    "        \n",
    "        self._width = width\n",
    "        self._length = length\n",
    "        self.color = color\n",
    "        \n",
    "        # for the sake of efficiency it is better to compute it one times in\n",
    "        # the init. If you don't, you will compute it each time you use the\n",
    "        # property\n",
    "        self._area = self.width * self.length\n",
    "   \n",
    "    @property\n",
    "    def area(self):\n",
    "        \"\"\" Area of the leaf \"\"\"\n",
    "        return self._area\n",
    "    \n",
    "    @property\n",
    "    def width(self):\n",
    "        \"\"\" leaf's width \"\"\"\n",
    "        return self._width\n",
    "\n",
    "    @property\n",
    "    def length(self):\n",
    "        \"\"\" leaf's width \"\"\"\n",
    "        return self._length"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "id": "34fc8eda-feca-4f28-a0ef-3bc86faba91e",
   "metadata": {},
   "outputs": [],
   "source": [
    "l = Leaf(4, 12)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "id": "1ec2180c-b819-4697-8422-06b8b9d398cf",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "can't set attribute\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    l.width = -5\n",
    "except AttributeError as error:\n",
    "    print(\"#ERROR#\", error)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 40,
   "id": "8554daeb-9359-4b7a-8a40-4a887a8a227f",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "can't set attribute\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    l.length = -5\n",
    "except AttributeError as error:\n",
    "    print(\"#ERROR#\", error)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "5887e859-aa72-4cfd-9916-e78c14b0d9b1",
   "metadata": {},
   "source": [
    "But it is still possible to modify hidden attributes"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 41,
   "id": "bab07702-fe4e-4513-b4e3-7f81d8ccec48",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'_width': 4, '_length': 12, 'color': 'green', '_area': 48}\n"
     ]
    }
   ],
   "source": [
    "print(vars(l))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 46,
   "id": "5b3e2330-05e6-424d-8f86-4c8efc42f51c",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'_width': -5, '_length': 12, 'color': 'green', '_area': 48}\n",
      "area = 48\n"
     ]
    }
   ],
   "source": [
    "l._width = - 5\n",
    "print(vars(l))\n",
    "print(\"area =\", l.area)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "4bdf4746-e6fc-4257-9c0d-108e63691118",
   "metadata": {},
   "source": [
    "## Define properties and setters\n",
    "\n",
    "We assume the following:\n",
    "\n",
    "* area is a property computed from instance data\n",
    "* width and length can be update but with control"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 49,
   "id": "0dcb56a9-2c42-4c81-90c5-9d29db887de4",
   "metadata": {},
   "outputs": [],
   "source": [
    "class Leaf:\n",
    "    \"\"\" This class represents a leaf's tree \"\"\"\n",
    "    \n",
    "    def __init__(self, width: float, length: float, color: str = \"green\"):\n",
    "        \n",
    "        self._width = width\n",
    "        self._length = length\n",
    "        self.color = color\n",
    "        \n",
    "        # for the sake of efficiency it is better to compute it one times in\n",
    "        # the init. If you don't, you will compute it each time you use the\n",
    "        # property\n",
    "        self._area = self.width * self.length\n",
    "   \n",
    "    @property\n",
    "    def area(self):\n",
    "        \"\"\" Area of the leaf \"\"\"\n",
    "        return self._area\n",
    "    \n",
    "    @property\n",
    "    def width(self):\n",
    "        \"\"\" leaf's width \"\"\"\n",
    "        return self._width\n",
    "    \n",
    "    @width.setter\n",
    "    def width(self, val):\n",
    "        \"\"\" check width and upadte self \"\"\"\n",
    "        if val > 0:\n",
    "            self._width = val\n",
    "            self._area = self._width * self._length\n",
    "        else:\n",
    "            raise ValueError(f\"Wrong width values: '{val}'\")\n",
    "\n",
    "    # other option to define property\n",
    "    def get_length(self):\n",
    "        \"\"\" leaf's width \"\"\"\n",
    "        return self._length\n",
    "    \n",
    "    def set_length(self, val):\n",
    "        \"\"\" check width and upadte self \"\"\"\n",
    "        if val > 0:\n",
    "            self._length = val\n",
    "            self._area = self._width * self._length\n",
    "        else:\n",
    "            raise ValueError(f\"Wrong width values: '{val}'\")\n",
    "    \n",
    "    length = property(get_length, set_length)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 57,
   "id": "e1e66333-988b-464e-86bd-a448f76ac0aa",
   "metadata": {},
   "outputs": [],
   "source": [
    "l = Leaf(4, 12)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 59,
   "id": "86caaf71-20b3-408f-bf0c-bf3c6c23c47e",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'_width': 5, '_length': 24, 'color': 'green', '_area': 120}     area = 120\n",
      "{'_width': 5, '_length': 24, 'color': 'green', '_area': 120}     area = 120\n",
      "{'_width': 5, '_length': 24, 'color': 'green', '_area': 120}     area = 120\n",
      "#ERROR# Wrong width values: '-1'\n"
     ]
    }
   ],
   "source": [
    "print(vars(l), \"    area =\", l.area)\n",
    "l.length = 24\n",
    "print(vars(l), \"    area =\", l.area)\n",
    "l.width = 5\n",
    "print(vars(l), \"    area =\", l.area)\n",
    "try:\n",
    "    l.width = -1\n",
    "except ValueError as error:\n",
    "    print(\"#ERROR#\", error)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8ff52eb3-737f-436e-a46a-d88675e92260",
   "metadata": {},
   "source": [
    "## Fast class writing \n",
    "\n",
    "There are several class factories in python that write some parts of the code for you. For\n",
    "example the special methods `__init__` or `__repr__` or others.\n",
    "\n",
    "### Use NamedTuple\n",
    "\n",
    "`namedtuple` is a very fast way to get a datacontainer with imutable fields (as tuples)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 71,
   "id": "4a363f8c-0fdb-4dd0-8259-8fde8dee519b",
   "metadata": {},
   "outputs": [],
   "source": [
    "from collections import namedtuple"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 102,
   "id": "db0662ca-0c08-4b74-a226-365cb80ae410",
   "metadata": {},
   "outputs": [],
   "source": [
    "Leaf = namedtuple(\"Leaf\", [\"width\", \"length\", \"color\"], defaults=[\"green\"])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 103,
   "id": "0b625522-b881-479e-adbc-e14da036f7cc",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "Leaf(width=4, length=12, color='green')"
      ]
     },
     "execution_count": 103,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l = Leaf(4, 12)\n",
    "l"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 104,
   "id": "6c41e5d4-3582-4905-8c98-233a00348b4a",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 104,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l2 = Leaf(4, 12)\n",
    "l == l2  # this comparison was not available in previous implementation."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 105,
   "id": "1d9df4a6-3ab5-4128-b041-018dea1daa4d",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(4, 12)"
      ]
     },
     "execution_count": 105,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.width, l.length"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 106,
   "id": "25482abf-dfff-4a86-bc1f-a5682410c496",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "4\n",
      "12\n",
      "green\n"
     ]
    }
   ],
   "source": [
    "for item in l:\n",
    "    print(item)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 107,
   "id": "c8a25596-e3f6-4b60-b981-db0eabf8d848",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "4\n",
      "12\n",
      "green\n"
     ]
    }
   ],
   "source": [
    "for i in range(3):\n",
    "    print(l[i])"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "3e8ac142-026a-4f78-aa65-8d51a62e3429",
   "metadata": {},
   "source": [
    "NamedTuple are immutable object. You cannot set attributes."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 109,
   "id": "468854e9-94ce-4b9c-802d-0a647afea296",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "can't set attribute\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    l.length = 5\n",
    "except AttributeError as error:\n",
    "    print(error)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 111,
   "id": "fa3407fa-45e2-4a0a-b1d3-ef0c41d7cd84",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "'Leaf' object has no attribute 'area'\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    l.area = l.length * l.width\n",
    "except AttributeError as error:\n",
    "    print(error)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "446566ef-ac47-4028-b12d-780954eb9e2c",
   "metadata": {},
   "source": [
    "NamedTuple is very fast but very basic. For example, here `area` is not available. You can however extend it:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 112,
   "id": "9e8b17f5-86a2-4e8a-8894-c068f740c649",
   "metadata": {},
   "outputs": [],
   "source": [
    "class Leaf(namedtuple(\n",
    "    \"Leaf\", [\"width\", \"length\", \"color\"], defaults=[\"green\"])):\n",
    "    \n",
    "    @property\n",
    "    def area(self):\n",
    "        return self.width * self.length"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 114,
   "id": "51f35f8b-cf6f-4c5b-9bc0-2bc0dd4c33c7",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "Leaf(width=4, length=12, color='green')"
      ]
     },
     "execution_count": 114,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l = Leaf(4, 12)\n",
    "l"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 115,
   "id": "29b346b7-63e6-4105-a373-8c471fa7e7e2",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "48"
      ]
     },
     "execution_count": 115,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.area"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "0fa3247e-d5ef-49db-ac19-1f7be00c9a80",
   "metadata": {},
   "source": [
    "### Dataclass Example\n",
    "\n",
    "The aim of dataclass is to be a container. By default, the aim is not to protect\n",
    "data. In the following attributed are thus editable."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 88,
   "id": "6f30ac4f-8867-41c8-b947-e191811cf0e5",
   "metadata": {},
   "outputs": [],
   "source": [
    "from dataclasses import dataclass, field"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 116,
   "id": "24531d86-4d38-4532-9d65-51331f087dec",
   "metadata": {},
   "outputs": [],
   "source": [
    "@dataclass\n",
    "class Leaf:\n",
    "    \"\"\" This class represents a leaf's tree \"\"\"\n",
    "    \n",
    "    width: float\n",
    "    length: float\n",
    "    color: str = \"green\"\n",
    "    \n",
    "    area: float = field(init=False)\n",
    "    \n",
    "    def __post_init__(self):\n",
    "        self.area = self.width * self.length"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 122,
   "id": "3b68cbce-ce3d-4c75-be02-be5a8a8336d4",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "Leaf(width=4, length=12, color='green', area=48)"
      ]
     },
     "execution_count": 122,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l = Leaf(4, 12)\n",
    "l"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 123,
   "id": "915cefe4-bc7f-41f5-b741-d360a7bbb876",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "48"
      ]
     },
     "execution_count": 123,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.area"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 124,
   "id": "a10c937a-4d8c-47f5-9e84-2b24b5862a01",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'width': 4, 'length': 12, 'color': 'green', 'area': 48}"
      ]
     },
     "execution_count": 124,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "vars(l)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 125,
   "id": "e9685940-3fb8-4649-8df2-2c9c3da417f3",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'width': 4, 'length': 2, 'color': 'green', 'area': 48}"
      ]
     },
     "execution_count": 125,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# you loose the control on attributed relationship\n",
    "l.length = 2\n",
    "vars(l)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "06a84fa0-859a-41ae-9c15-17c86dee38ea",
   "metadata": {},
   "source": [
    "### Kind of Dataclass with validation\n",
    "\n",
    "Fine tuning of container classes can be achieve using pydantic `BaseModel`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 143,
   "id": "d213b50a-fb2e-4cc8-a98e-9576a4e87678",
   "metadata": {},
   "outputs": [],
   "source": [
    "from enum import Enum\n",
    "from pydantic import BaseModel, NonNegativeFloat, ValidationError, validator"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 156,
   "id": "3ed3bc76-74eb-46c5-8e82-164224b82ff3",
   "metadata": {},
   "outputs": [],
   "source": [
    "class ColorChoice(str, Enum):\n",
    "    green = \"green\"\n",
    "    very_green = \"very_green\"\n",
    "    so_green = \"so_green\"\n",
    "\n",
    "class Leaf(BaseModel):\n",
    "    width: NonNegativeFloat\n",
    "    length: NonNegativeFloat\n",
    "    color: ColorChoice = ColorChoice.green\n",
    "    \n",
    "    @validator(\"length\")\n",
    "    def length_lt_width_validation(cls, v, values):\n",
    "        if v < values[\"width\"]:\n",
    "            raise ValueError(f\"Length must be larger than width.\")\n",
    "        else:\n",
    "            return v\n",
    "\n",
    "    @property\n",
    "    def area(self):\n",
    "        return self.width * self.length"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 148,
   "id": "b413e670-b09d-4fe1-bb7b-01d91ba8228c",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "Leaf(width=3.0, length=8.0, color=<ColorChoice.green: 'green'>)"
      ]
     },
     "execution_count": 148,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l = Leaf(width=3, length=8)\n",
    "l"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 149,
   "id": "c292081f-b16d-4a81-8f1e-55283fef83e0",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "24.0"
      ]
     },
     "execution_count": 149,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.area"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 138,
   "id": "76e8ca7e-e918-434e-b803-8793ac33f085",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1 validation error for Leaf\n",
      "width\n",
      "  ensure this value is greater than or equal to 0 (type=value_error.number.not_ge; limit_value=0)\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    Leaf(width=-2, length=2)\n",
    "except ValidationError as error:\n",
    "    print(error)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 153,
   "id": "3b454c4e-4e5a-441e-a0b9-ec35791f0537",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1 validation error for Leaf\n",
      "length\n",
      "  Length must be larger than width. (type=value_error)\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    Leaf(width=12, length=2)\n",
    "except ValueError as error:\n",
    "    print(error)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 157,
   "id": "0cbe2d6e-869e-4eb9-9c9d-bb7b82218b32",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'width': 3.0, 'length': 8.0, 'color': <ColorChoice.green: 'green'>}"
      ]
     },
     "execution_count": 157,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.dict()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 158,
   "id": "d2f30713-aa7f-48ac-a707-2277db11ff6f",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'{\"width\": 3.0, \"length\": 8.0, \"color\": \"green\"}'"
      ]
     },
     "execution_count": 158,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "l.json()"
   ]
  }
 ],
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