Function Overload Signatures vs Implementation

What this Python function overload interview question tests

This is a hard question on Python's typing system, specifically the distinction between @overload decorator signatures and actual implementation. It probes whether a candidate understands how static type checkers like mypy interpret overload declarations versus how the Python runtime actually executes code.

The question rewards deep knowledge of Python's typing conventions: why overload signatures exist, what constraints they impose, and how they interact with a real implementation function. Candidates must reason about the contract between the type checker (which reads all overload variants) and the runtime (which only sees the final, non-decorated implementation). This matters because misuse of @overload can pass a type checker while breaking at runtime, or vice versa.

• Separation of type-checker concerns from runtime execution
• Overload declaration order and specificity
• The relationship between overload stubs and concrete implementation
• Common pitfalls in overload definition