Core Python Programming

11.5. Formal Arguments

A Python function's set of formal arguments consists of all parameters passed to the function on invocation for which there is an exact correspondence to those of the argument list in the function declaration. These arguments include all required arguments (passed to the function in correct positional order), keyword arguments (passed in- or out-of-order, but which have keywords present to match their values to their proper positions in the argument list), and all arguments which have default values which may or may not be part of the function call. For all of these cases, a name is created for that value in the (newly-created) local namespace and can be accessed as soon as the function begins execution.