Mappings

Dictionaries

employee = {
    "name": "Alice",
    "position": "Software Engineer",
    "skills": ["Python", "JavaScript", "SQL"],
    "contact": {
        "email": "alice@example.com",
        "phone": "555-1234"
    }
}

You will use dicts even if you don’t want to:

function keyword arguments
class attributes

Mapping extras: Collections

collections.ChainMap
collections.defaultdict
(ordered dict)

Recipe: EAFP - Easier to Ask for Forgiveness than Permission

This common Python coding style assumes the existence of valid keys or attributes and catches exceptions if the assumption proves false. This clean and fast style is characterized by the presence of many try and except statements.

how to deal with this:

validate structure in advance
collections.defaultdict
subclass collections.userdict

Recipe: The problem

It’s definition: mutable. It can be hard to trace back.

think twice, do I really need a mutable object?
type.MappingProxyType

Recipe: dict vs named tuple vs dataclass

dict to dataclass

from dataclasses import dataclass
import requests

@dataclass
class Pokemon:
    weight: int
    name: str
    order: int

j = requests.get("https://pokeapi.co/api/v2/pokemon/bulbasaur").json()
bulba = Pokemon(**{k: j[k] for k in ["weight", "name", "order"]})

#python