Model an inventory item with validation

Python data engineering interview problem. Difficulty: intermediate. Pattern: OOP. About 15 minutes. Part of the Pro drill bank.

Inventory items cannot exist with a negative quantity. Construction should reject bad data; a helper may return None for callers that prefer not to catch exceptions.

An inventory system must never hold an item with a negative quantity. The class should refuse to be created with a bad quantity, and a safe helper should turn that refusal into None. Write a class InventoryItem(sku, qty) that raises ValueError if qty is negative. Give it a method receive(n) that adds n to the quantity and raises ValueError if n is 0 or less. Also write safe_make(sku, qty) that returns {'sku': ..., 'qty': ...} for a good item and None when the item cannot be created. Write safe_make(sku, qty). safe_make('A', 2) returns {'sku': 'A', 'qty': 2}. safe_make('A', -1) returns None, because a negative quantity is not allowed. The starter file already has the function name and its print lines. Keep them and fill in the body.

Requirements

• InventoryItem rejects a negative qty with ValueError.
• receive(n) adds to qty and rejects n <= 0.
• safe_make returns a dictionary for valid items.
• safe_make returns None instead of raising.

Constraints

• Zero is a valid quantity.
• safe_make must catch the error and not let it escape.

Examples

Input: safe_make('A', 2) Output: {'sku': 'A', 'qty': 2} This input follows the stated rules and produces this output.

Topics: lakebench, python, OOP.

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