default parameter values python provides means for functions to support more than one possible calling signature such function is said to be polymorphic (which is greek for "many forms"most notablyfunctions can declare one or more default values for parametersthereby allowing the caller to invoke function with varying numbers of actual parameters as an artificial exampleif function is declared with signature def foo(ab= = )there are three parametersthe last two of which offer default values caller is welcome to send three actual parametersas in foo( )in which case the default values are not used ifon the other handthe caller only sends one parameterfoo( )the function will execute with parameters values = = = if caller sends two parametersthey are assumed to be the first twowith the third being the default thusfoo( executes with = = = howeverit is illegal to define function with signature such as bar(ab= cwith having default valueyet not the subsequent cif default parameter value is present for one parameterit must be present for all further parameters as more motivating example for the use of default parameterwe revisit the task of computing student' gpa (see code fragment rather than assume direct input and output with the consolewe prefer to design function that computes and returns gpa our original implementation uses fixed mapping from each letter grade (such as -to corresponding point value (such as while that point system is somewhat commonit may not agree with the system used by all schools (for examplesome may assign an agrade value higher than thereforewe design compute gpa functiongiven in code fragment which allows the caller to specify custom mapping from grades to valueswhile offering the standard point system as default def compute gpa(gradespoints= : : : : : : : : : : : : })num courses total points for in gradesif in pointsa recognizable grade num courses + total points +points[greturn total points num courses code fragment function that computes student' gpa with point value system that can be customized as an optional parameter