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Looking Things Up in a Dictionary

~8 mincode completion

A dictionary maps keys to values. Where a list is "the third item", a dictionary is "the item called price".

item = {"name": "widget", "price": 9.99, "stock": 3}

item["name"]        # "widget"
item["price"]       # 9.99
"stock" in item     # True
len(item)           # 3

Asking for a key that is not there raises KeyError. When a key might be missing, use .get(), which returns None instead of raising, or a default you choose:

item["colour"]              # KeyError: 'colour'
item.get("colour")          # None
item.get("colour", "grey")  # "grey"

That default argument is the whole point of .get(). It replaces this:

if "colour" in item:
    colour = item["colour"]
else:
    colour = "grey"

Your task:

Write stock_level(inventory, product) that returns how many of product are in stock. If the product is not in the dictionary at all, return 0 rather than raising an error.

Example Tests

A product that exists returns its count

Input: {"product":"widget","inventory":{"gizmo":7,"widget":3}}

Expected: 3

A different existing product returns its own count

Input: {"product":"gizmo","inventory":{"gizmo":7,"widget":3}}

Expected: 7

A missing product returns 0 instead of raising KeyError

Input: {"product":"sprocket","inventory":{"widget":3}}

Expected: 0

Python

def stock_level(inventory, product):
    """
    Look up a product's stock count.

    Args:
        inventory: a dict mapping product name -> count
        product: the product name to look up

    Returns:
        The count, or 0 if the product is not in the inventory.
    """
    # YOUR CODE HERE
    pass

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