pydantic.py

import json
import pydantic
from typing import Optional , List

books_list = '''[
  {
    "isbn_10": "1593279509",
    "isbn_13": "1593279509",
    "title": "Eloquent JavaScript, Third Edition",
    "subtitle": "A Modern Introduction to Programming",
    "author": "Marijn Haverbeke",
    "publisher": "No Starch Press",
    "price": 47.2
  },
  {
    "isbn_10": "1491943533",
    "isbn_13": "1491943533",
    "title": "Practical Modern JavaScript",
    "subtitle": "Dive into ES6 and the Future of JavaScript",
    "author": "Nicolás Bevacqua",
    "publisher": "O'Reilly Media",
    "price": 33.4
  },
  {
      "isbn_10": "1491943533",
    "isbn_13": "1491943533",
    "title": "Understanding ECMAScript 6",
    "subtitle": "The Definitive Guide for JavaScript Developers",
    "author": "Nicholas C. Zakas",
    "publisher": "No Starch Press",
    "price": 35.2
  },
  {
    "isbn_10": "1449365035",
    "isbn_13": "1449365035",
    "title": "Speaking JavaScript",
    "subtitle": "An In-Depth Guide for Programmers",
    "author": "Axel Rauschmayer",
    "publisher": "O'Reilly Media",
    "price": 46.0
  },
  {
    "isbn_10": "1449331818",
    "isbn_13": "1449331818",
    "title": "Learning JavaScript Design Patterns",
    "subtitle": "A JavaScript and jQuery Developer's Guide",
    "author": "Addy Osmani",
    "publisher": "O'Reilly Media",
    "price": 25.4
  },
  {
    "isbn_10": "8602477429",
    "isbn_13": "8602477429",
    "title": "You Don't Know JS Yet",
    "subtitle": "Get Started",
    "author": "Kyle Simpson",
    "publisher": "Independently published",
    "price": 14.3
  }]'''


class ISBN10FormatError(Exception):
    def __init__(self , value:str , message:str) -> None:
        self.value=value
        self.message=message
        super().__init__(message)

class ISBNNotFoundError(Exception):
     def __init__(self , values:str , message:str) -> None:
        self.values=values
        self.message=message
        super().__init__(message)   

class Book(pydantic.BaseModel):
    title : str
    author : str
    publisher : str
    price : float
    isbn_10: Optional[str]
    isbn_13 : Optional[str]
    subtitle : Optional[str]

    # ADDING VALIDATION FOR PYDANTIC

    @pydantic.validator("isbn_10")
    @classmethod
    def isbn_10_valid(cls,value):
        chars = [c for c in value if c in  '0123456789xX']
        if len(chars) !=10:
            raise ISBN10FormatError(value=value,message="ISBN10 Should be 10 digits")
        return value
    
    @pydantic.root_validator(pre=True)
    @classmethod
    def isbn_10_or_isbn_13_present(cls,values):
        if 'isbn_10' not in values and 'isbn_13' not in values:
            raise ISBNNotFoundError(values=values,message='ATLEAST ONE ISBN MUST BE PRESENT')
        return values


    class Config:
        '''MAKES BOOK IMMUTABLE'''
        allow_mutation = False
        anystr_lower = True # makes any string value lower


def main() -> None:
    data = json.loads(books_list)
    books:List[Book] = [Book(**item) for item in data]
    print(books[0]) # PYDANTIC MODEL , USE dir(books) to get the properties and methods

    
    ''' 
    books[0] is a pydantic model and has methods like , books[0].to_dict() , books[0].to_json() and to_dict() has some arguments that can be passed like include (includes only that) and exclued(exclues that particular item in json dict)etc.

    '''

if __name__=='__main__':
    main()