Functions

Functions let us run a block of code by calling the function's name. A function may or may not get parameters and return values. We can use a single function as many times as we want!
Some advantages of using functions:

Avoid code duplication
More readable - functions with self-explanatory names
Much easier to modify (no code duplication)
Much easier to debug

Defining a Function

A function is defined using the def keyword. Evry function must have a unique name. The name is followed by parentheses.

The Syntax:

def function_name(parameters):
Code Block


            #Function

            def my_func():
                print("My very first python function!")

The function in the example above doesn't get any parameters. When we call it, the function prints the same phrase.

Add Arguments

Data can be passed into functions as arguments. Arguments are specified after the function name, inside the parentheses and separated by a comma.


            #Arguments

            def my_func(a, b):
                print(a, "comes before", b)
            
            my_func("The chicken", "the egg")

Calling a Function

To call a function, use the function name followed by parenthesis:


            #Function

            def my_func():
                print("My very first python function!")
            
            my_func()

Keyword Arguments

You can send arguments with the key = value syntax. This method is called keyword arguments.


            #Function

            def my_func(a, b, c):
                print(a)
                print(b)
                print(c)
            
            my_func(c=5, a=3, b=4)

Default Argument Value

You can create a function with default arguments. When calling the function without argument, it uses the default value.


            #Default Argument Value

            def my_func(a="Hello, World!"):
                print(a)

            my_func()
            my_func("Hello, Python!")

Arbitrary Keyword Arguments

What if we want to use arbitrary number of arguments? Python provides several methods to do so:

Arbitrary Arguments (*args)

If you do not want to predetermine the exact number of arguments the functions gets, add an asterisk * before the parameter name in the function definition. Arbitrary Arguments are often shortened to *args in Python documentations.


            #*args

            def my_func(a, b, *args):
                print(a)
                print(b)
                for i in args:
                    print(i)
            
            my_func(1, 2, 3, 4, 5)

Arbitrary Keyword Arguments (**kwargs)

If you do not want to predetermine the exact number of arguments the functions gets, add two asterisks ** before the parameter name in the function definition. Arbitrary Keyword Arguments are often shortened to **kwargs in Python documentations. This way you can send an arbitrary number of key = value arguments.


            #**kwargs

            def print_last_name(**kwargs):
                for first_name, last_name in kwargs.items():
                    print("{first_name}'s last name is {last_name}".format(first_name=first_name, last_name=last_name))
            
            print_last_name(Franz="Schubert", Robert="Schumann", Frederic="Chopin")

Exercise

Create a function that prints out your name.
Give it a self-explanatory name.
Call the function a couple of times.


            #Write your code here

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