7.2. Defining Functions - How

The same syntax we use to name procedures can be used to define new functions. The only difference is that a function will return a value. To return a value from a function use the Python keyword return followed by the value to return. The value can be a literal value like 3.14 or "Hello there", but will generally be a variable that we calculated within the function.

This is a definition for a function that accepts the lengths of the two legs (shorter sides) of a right triangle as its parameters and calculates the length of the hypotenuse (long side). The final value that it computes - sideC is what gets returned.

def hypotenuse_length(sideA, sideB): # sideA and sideB are our inputs aSquared = math.pow(sideA, 2) bSquared = math.pow(sideB, 2) sideC = math.sqrt(aSquared + bSquared) # this is the final answer return sideC # we return it

Of course, running it right now does nothing. Just like a procedure definition, a function definition does not cause anything to happen on its own. It is only the instructions for what to do when someone calls hypotenuse_length. So let’s add a call to the function. This working program asks for the lengths of two sides from the user and then uses those two values a and b to call hypotenuse_length.

def hypotenuse_length(sideA, sideB): aSquared = math.pow(sideA, 2) bSquared = math.pow(sideB, 2) sideC = math.sqrt(aSquared + bSquared) return sideC # main part of program import math a = float(input("Enter side a")) b = float(input("Enter side b")) c = hypotenuse_length(a, b) print("The length of side c is", c)

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