Costing & Pricing¶

Costing a recipe¶

Provide purchase data — any object satisfying the PurchasedItem protocol works. Purchase is a built-in Pydantic model for convenience.

from decimal import Decimal
from wright import Purchase, calculate_recipe_cost, get_top_cost_drivers

groceries = [
    Purchase(name="Flour", quantity=1000, unit="g", price=Decimal("3.99")),
    Purchase(name="Butter", quantity=500, unit="g", price=Decimal("5.49")),
]

cost = calculate_recipe_cost(recipe, groceries)

calculate_recipe_cost returns a RecipeCost with:

Attribute	Type	Description
`.total_cost_range`	`PriceRange`	min/max total cost for the recipe
`.cost_per_serving_range`	`PriceRange`	min/max cost divided by servings
`.ingredient_costs`	`list[IngredientCost]`	per-ingredient cost breakdown

print(cost.total_cost_range)
# → PriceRange(min_price=Decimal('1.99'), max_price=Decimal('1.99'))
print(cost.cost_per_serving_range.midpoint)
# → Decimal('0.20')

Top cost drivers¶

drivers = get_top_cost_drivers(cost, n=3)
# → list[IngredientCost] sorted by price_descending
for d in drivers:
    print(f"{d.ingredient_name}: ${d.price_range.midpoint}")

Unit conversion¶

Recipes use grams. Purchases use pounds. wc_right handles conversion transparently:

# Recipe: 170g salmon. Supplier: 454g at $14.99
# → 170/454 * $14.99 = $5.61

For volume-to-weight conversions (e.g., olive oil), provide density data:

density_data = {"liquids": {"Olive Oil": 0.91}}  # 0.91 g/ml
cost = calculate_recipe_cost(recipe, groceries, density_data=density_data)

For dry ingredients (spices, sugar), use volume weights:

density_data = {
    "volume_weights": {
        "Cinnamon": {"tsp": 2.6, "tbsp": 7.8},
        "Sugar": {"tsp": 4.2, "tbsp": 12.5, "cup": 200.0},
    }
}

Pricing¶

Two strategies, one idea: cover costs and leave margin.

from wright import margin_price, multiplier_price

cost = Decimal("2.00")

margin_price(cost, Decimal("0.67"))  # → Decimal('6.06')  — 67% margin
margin_price(cost, 0.67)  # → Decimal('6.06')  — float also works
multiplier_price(cost, 3)  # → Decimal('6.00')  — 3× cost

Every pricing function returns a Decimal. No formatting or rounding inside the library — do that at your UI layer.