Preserve function metadata when creating wrapper functions (e.g., decorators).

Indicates that the wrapper should retain the original function's identity and documentation.

When writing a decorator that wraps a function and you want the wrapper to appear as the original function for introspection, help(), or logging.

Used inside decorator definitions, especially when creating wrappers that need to mimic the wrapped function's metadata.

functools.update_wrapper(wrapper, func, assigned=tuple_of_attributes)

wrapper func assigned

• functools wraps decorator __module__ __name__ __qualname__ __doc__ __annotations__

• functools.wraps manual attribute copying

Forgetting to copy __annotations__, losing type hints; using functools.wraps incorrectly by omitting the function argument.

functools.wraps (a convenience wrapper that calls update_wrapper internally) manual attribute copying (error-prone, verbose)

Using update_wrapper without assigned attributes may copy too much (e.g., __dict__) causing unexpected shared state.

• functools
• decorators
• function metadata

The assigned tuple controls which attributes are copied; omitting __annotations__ loses type hints in Python 3.x.

Signals to readers and tools that the wrapper is transparent with respect to the wrapped function's interface.

Think of 'updating the wrapper's resume' with the original function's details.

functools.wraps is a convenience function that internally calls update_wrapper with a default set of attributes.

functools.wraps (more convenient decorator form)