pavlova is a library that assists in mapping an unknown input into a dataclass.
from datetime import datetime from dataclasses import dataclass from pavlova import Pavlova @dataclass class Input: id: int name: str date: datetime Pavlova().from_mapping({ 'id': 10, 'name': 100 'date': '2018-08-10', }, Input) # Input(id=10, name='100', date=datetime.datetime(2018, 8, 10, 0, 0))Pavlova was born out of frustration with the lack of typing support for existing deserialization libraries. With the introduction of dataclasses in Python 3.7, they seemed like the perfect use for defining a deserialization schema.
Parsing of booleans, datetimes, floats, ints, strings, decimals, dictionaries, enums, lists are currently supported.
There are more parsers to come, however to implement your own custom parser, simply implement PavlovaParser in pavlova.parsers, and register it with the Pavlova object with the register_parser method.
pip install pavlovafrom dataclasses import dataclass, asdict from flask import Flask, jsonify from pavlova.flask import FlaskPavlova pavlova = FlaskPavlova() app = Flask(__name__) @dataclass class SampleInput: id: int name: str @app.route('/post', methods=['POST']) @pavlova.use(SampleInput) def data(data: SampleInput): data.id = data.id * len(data.name) return jsonify(asdict(data)) app.run()There are a couple of different ways to implement new types for parsing in pavlova. In general, the process is to add a parser a specific type. For validation you should raise a TypeError or ValueError.
The first one, is creating a new type that extends an existing base type. Here is an example on how to implement an Email type, which is a string but performs validation.
from pavlova import Pavlova from pavlova.parsers import GenericParser class Email(str): def __new__(cls, input_value: typing.Any) -> str: if isinstance(input_value, str): if '@' in input_value: return str(input_value) raise ValueError() raise TypeError() pavlova = Pavlova() pavlova.register_parser(Email, GenericParser(pavlova, Email))Another way, is to implement your own pavlova parser, rather than using your the built in GenericParser parser.
import datetime from typing import Any, Tuple import dateparser from pavlova import Pavlova from pavlova.parsers import PavlovaParser class DatetimeParser(PavlovaParser[datetime.datetime]): "Parses a datetime" def parse_input(self, input_value: Any, field_type: Type, path: Tuple[str, ...]) -> datetime.datetime: return dateparser.parse(input_value) pavlova = Pavlova() pavlova.register_parser(datetime.DateTime, DatetimeParser(pavlova))Pavlova is only supported on Python 3.6 and higher. With Python 3.6, it will install the dataclasses module. With Python 3.7 and higher, it will use the built-in dataclasses module.
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