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.

Model InventoryItem so invalid quantities cannot be constructed, and implement safe_make as a non-throwing wrapper.

Requirements

• qty < 0 is invalid at construction.
• receive(n) rejects n <= 0.
• safe_make returns a dict or None instead of raising.

Constraints

• Function safe_make(sku, qty).
• Callers of the class still see exceptions.
• safe_make is the soft path.

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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