5.9. Parameters and arguments

Some of the built-in functions we have seen require arguments. For example, when you call math.sin, you pass a number as an argument. Some functions take more than one argument: math.pow takes two, the base and the exponent.

Inside the function, the arguments are assigned to variables called parameters. Here is an example of a user-defined function that takes an argument:

def print_twice(bruce):

This function assigns the argument to a parameter named bruce. When the function is called, it prints the value of the parameter (whatever it is) twice.

This function works with any value that can be printed.

Activity: CodeLens 5.9.2 (functParam_codelens1)

The same rules of composition that apply to built-in functions also apply to user-defined functions, so we can use any kind of expression as an argument for print_twice:

Activity: CodeLens 5.9.3 (functParam_codelens2)

The argument is evaluated before the function is called, so in the examples the expressions 'Spam '*4 and math.cos(math.pi) are only evaluated once.

You can also use a variable as an argument:

Activity: CodeLens 5.9.4 (functParam_codelens3)

The name of the variable we pass as an argument (michael) has nothing to do with the name of the parameter (bruce). It doesn’t matter what the value was called back home (in the caller); here in print_twice, we call everybody bruce.

Construct a block of code with four functions, defined in this order: printName, printGPA, printAttendance, printStudentInfo. printStudentInfo should call the other three functions which will print all of the student’s information. Be mindful of indentation!

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