In Python, if you define a variable inside a function, it can only be used inside the function. Variables that are only defined inside a function are known as local variables.

For example, take a look at the FtoC() function from the Return Values section:

def FtoC(degf):
        degc = (degf - 32) / 1.8
        return degc

This function defines a variable, named degc, that contains the converted Celsius temperature. This variable is only defined inside the FtoC() function; you cannot use it elsewhere. For instance, the following code is not legal:

def FtoC(degf):
        degc = (degf - 32) / 1.8
        return degc

FtoC(98.6)
print degc

If you run this program, Python flags the print statement as an error, stating that degc is not defined.