Filtering Dictionary in Python

using_filterable_dict.py

from typing import Dict

# Helper function to generate dict object
def get_menu() -> Dict[str, dict]:
    return {
        "TIMMY_BLACK": {
            "item": "Timmy's Coffee Barista's Black",
            "sugar_free": True,
            "with_milk": False,
        },
        "TIMMY_LATTE": {
            "item": "Timmy's Coffee Latte",
            "sugar_free": True,
            "with_milk": False,
        },
        "TIMMY_SWEETENED_LATTE": {
            "item": "Timmy's Coffee Latte - Sweetened",
            "sugar_free": True,
            "with_milk": True,
        },
        "TIMMY_SIGNATURE_CARAMEL": {
            "item": "Timmy's Signature - Caramel Latte",
            "sugar_free": None,  # Unknown
            "with_milk": True,
        }
    }

# Our dict subclass
class FilterableDict(dict):
    def __init__(self, *args, **kwargs):
        dict.__init__(self, *args, **kwargs)
    def filter(self, predicate):
        key_copy = tuple(self.keys())
        for k in key_copy:
            if predicate(k, self.get(k)):
                del self[k]
        return self
    def __repr__(self):
        return "FilterableDict({})".format(super().__repr__())


coffees = FilterableDict(get_menu())

coffees   # FilterableDict({...})

len(coffees)    # 4

sugar_free_filter = lambda _, v: not v["sugar_free"]

coffees.filter(sugar_free_filter)

len(coffees)     # 3