Template Method Example: Importing CSV and JSON Files

import csv
import io
import json
from abc import ABC, abstractmethod
from typing import final

Row = dict[str, str]


class Importer(ABC):
    def __init__(self) -> None:
        self.stored: list[Row] = []

    @final
    def run(self, source: str) -> None:
        text = self.open(source)
        rows = self.parse(text)
        valid = [row for row in rows if self.validate(row)]
        self.store(valid)
        print(f"{type(self).__name__}: {len(rows)} read, {len(valid)} stored")

    def open(self, source: str) -> str:
        return source.strip()

    @abstractmethod
    def parse(self, text: str) -> list[Row]: ...

    def validate(self, row: Row) -> bool:
        return True

    def store(self, rows: list[Row]) -> None:
        self.stored.extend(rows)


class CsvImporter(Importer):
    def parse(self, text: str) -> list[Row]:
        return list(csv.DictReader(io.StringIO(text)))


class JsonImporter(Importer):
    def parse(self, text: str) -> list[Row]:
        return json.loads(text)

    def validate(self, row: Row) -> bool:
        return bool(row.get("email"))


CsvImporter().run("""
name,email
Sam,[email protected]
Ali,[email protected]
""")
JsonImporter().run("""
[{"name": "Kim", "email": "[email protected]"}, {"name": "Lee", "email": ""}]
""")