If your program performs a task more than once, you can define this task as a separate chunk of code. This chunk of code is known as a function.

Here is a simple example of a function and how to use it:

# convert a patient temperature from Fahrenheit to Celsius
def FtoC(degf):
        degc = (degf - 32) / 1.8
	return degc

tempF = 50.0
tempC = FtoC(tempF)

The following sections provide more details on how to define and use functions, and how to use global variables inside functions: