Preserving signature for introspection

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Accepted Answer

functools.wraps does more than copy __name__ and __doc__. It also sets __wrapped__ on the wrapper, pointing at the original function. inspect.signature follows the __wrapped__ chain until it finds a function without it, then returns that function's signature. This matters enormously for tools that validate arguments at runtime (FastAPI, Pydantic, pytest fixtures, dataclasses). If you write a wrapper that changes the actual accepted arguments - say, it pops a 'db' argument before delegating - you need to either update the signature manually or use a library like 'decorator' that rewrites the signature object itself. Most developers assume @wraps is enough and discover the gap only when a framework introspects their function and breaks.