Functions with parameters

A parameter is a special kind of variable, used in a function to refer to a piece of data provided as input to the function.

Let's see some examples of functions that have parameters:

String as input parameter

def say_hello(name):
        print ("Hello! " + name)

# call the function with required input data
say_hello('Emily')    # Hello! Emily

Run the function by calling it's name and providing necessary input values to it's parameters. In the above example, string value 'Emily' is provided to parameter name.

Note that in the print line, we input "Hello! " + name, the plus + sign indicates that we are going to use name as a string since only a string can be added to string "Hello! ".

Number as input parameter

def add_two(x):
    print(2 + x)

# call the function
add_two(10)     # console result: 12
add_two(20)     # console result: 22

Inside the function definition, print(2+x) requires that x needs to be a number.