Function object

A function object is a callable runtime object representing a function together with the context needed to execute it. In CPython, a Python-defined function object refers to a code object, its defining global namespace, default argument values and any captured bindings. The code object alone does not contain all this context.^[ref]

For example, a factory make_adder(k) can return a nested function computing x+k. Calling the factory with two and five can produce function objects sharing one code object but retaining different values of k through their programming closures. Their results on input ten are twelve and fifteen. This explains why identifying compiled instructions is insufficient to identify a callable's behavior.