Parameters and Return Values

A parameter is a name that receives an input when a function is called.

value is a parameter. It refers to whatever argument is passed during the call:

Output:

8
14

Arguments and Parameters

In this call:

double(4)

4 is the argument.

In this definition:

def double(value):

value is the parameter.

The argument supplies a value. The parameter is the local name that receives it.

return Sends a Value Back

This function returns a value:

The caller can print it:

print(add(2, 3))

or store it:

print Is Not return

This function prints a value but returns None:

This function returns a value:

The distinction matters. A returned value can be used by later code.

print versus return

The first function only prints. The second returns a value that can be reused.

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Ready to run.

Printing Is Not Returning

Expecting a printed value to be reusable:

The second print shows None, because show_total() did not return a value.

Exercise: Returned value

What value does this function call return?

Compute it first, then check your number.

HintBind arguments to parameters

In this call, weight receives 3 and value receives 4.

SolutionThe function returns twelve

Substitute the arguments into weight * value: 3 * 4 is 12, so the call returns 12.

Parameters Enter and Return Values Leave

Parameters receive inputs. return sends a value back. Prefer returning values when later code needs to use the result.