Schema Validation

Pydantic

At some point it might be interesting to make sure that the YAML we are reading follows some standards. That is why we have introduced the ability to pass a schema our file needs to follow.

This feature is supported by Pydantic, and not only helps us to validate the schema, but even updating the values we're reading with Optionals and defaults.

Let's continue working with our example YAML:

title: "Lévy the cat"
colors:
  - "black"
  - "white"
hobby:
  eating:
    what: "anything"
friends:
  {% set friends = [ "cartman", "lima" ] %}
  {% for friend in friends %}
  - name: ${ friend }
    type: "cat"
  {% endfor %}

We can get this running as

from typing import Optional, List, Dict

from levy.config import Config
from pydantic import BaseModel


class Friends(BaseModel):
    name: str
    type: str
    fur: str = "soft"

class Kitten(BaseModel):
    title: str
    age: Optional[int]
    colors: List[str]
    hobby: Dict[str, Dict[str, str]]
    friends: List[Friends]

cfg = Config.read_file("<file>", datatype=Kitten)

Note how this adds even another layer of flexibility, as after reading the config we will have all the data we might require available to use.

// We have the data attribute now hosting the data class
$ cfg.data
Kitten(title='Lévy the cat', age=None, colors=['black', 'white'], hobby={'eating': {'what': 'anything'}}, friends=[Friends(name='cartman', type='cat', fur='soft'), Friends(name='lima', type='cat', fur='soft')])

// Optional values become None
$ cfg.age
None

// We have missing values with their default
$ cfg.friends.lima.fur
"soft"