example7.ipynb

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   "source": [
    "# Example 7 - Validation\n",
    "\n",
    "Data classes were not designed with extensive validation in mind. However, we can do some validation in the \\_\\_post\\_init\\_\\_ method:"
   ]
  },
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   "id": "e2bfc525-5efd-4c16-bc70-e6a558891354",
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   "source": [
    "from dataclasses import dataclass\n",
    "import yaml"
   ]
  },
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   "source": [
    "@dataclass \n",
    "class City:\n",
    "    name: str\n",
    "    latitude: float\n",
    "    longitude: float\n",
    "    \n",
    "    def __post_init__(self):\n",
    "        \"Do some validation.\"\n",
    "        assert type(self.name) is type('') and len(self.name) > 0, \"Name must be a non-empty string.\"\n",
    "        assert self.latitude <= 90.0 and self.latitude >= -90.0, \"Latitude must fall in the range -90.0 to 90.0\"\n",
    "        assert self.longitude <= 180.0 and self.longitude >= -180.0, \"Longitude must fall in the range -180.0 to 180.0\"      "
   ]
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    "\\_\\_post\\_init\\_\\_ is called by the \\_\\_init\\_\\_ method of data class objects."
   ]
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   "execution_count": null,
   "id": "3ac0752f-c94f-470d-badf-22f81ec2bcb2",
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   "outputs": [],
   "source": [
    "c = City(42, latitude=40.0, longitude=-110)"
   ]
  },
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   "id": "f770d007-46e1-402c-a576-c5a920b084ca",
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   "source": [
    "c = City(\"Denver\", latitude=140.0, longitude=-110)"
   ]
  },
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   "execution_count": null,
   "id": "64afa585-acd2-4ccc-a249-7b249071c3c1",
   "metadata": {},
   "outputs": [],
   "source": [
    "c = City(\"Denver\", latitude=40.0, longitude=-210)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "b67c275c-41cd-416f-b645-14c2669f0b8c",
   "metadata": {},
   "source": [
    "This technique has some limitations however:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "2d0c9380-cfb2-45a6-a108-d5c4d88fec14",
   "metadata": {},
   "outputs": [],
   "source": [
    "broken_city_object = yaml.load( open(\"broken_city_object.yaml\",\"r\"), Loader=yaml.Loader )\n",
    "broken_city_object"
   ]
  },
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