Programming

Python Programming Essentials

Function Overview

• Definition of a Function: A block of organized, reusable code that performs a single, related action.

• Benefits:

  • Enhances modularity of applications.

  • High degree of code reusability.

Defining a Function

• Function blocks start with the keyword def followed by the function name and parentheses ( ).

• Input Parameters:

  • Arguments can be placed within the parentheses.

  • Can define parameters inside parentheses.

• Code Block:

  • Begins with a colon : and must be indented.

• Return Statement:

  • return [expression] exits a function and can return an expression to the caller.

  • A return with no arguments returns None.

Defining and Calling a Function

• Example:

  def greet:
      print("hi")
  greet();

Function with Parameter

• Example:

  def greet(name):
      print("hi" + name)
  greet('John');

Function with Default Value Parameters

• Example:

  def greet(name="John Doe"):
      print("hi" + name)
  greet();
  greet("Ana");
  def my_function(child3, child2, child1):
      print("The youngest child is " + child3)
  my_function(child1="Emil", child2="Tobias", child3="Linus")

Function with Return

• Example:

  def greet():
      return "Hello"
  print(greet());
  def my_function(x):
      return 5 * x
  print(my_function(3))
  print(my_function(5))
  print(my_function(9))
  def myfunction():
      pass

Arbitrary Arguments, *args

• Definition: Allows you to pass a variable number of arguments.

• Example:

  def my_function(*kids):
      print("The youngest child is " + kids[2])
  my_function("Emil", "Tobias", "Linus")

• Note: Use a * before the parameter name to receive a tuple of arguments.

Arbitrary Arguments, **kwargs

• Definition: Allows passing a variable number of keyword arguments.

• Example:

  def my_function(**kid):
      print("His last name is " + kid["lname"])
  my_function(fname="Tobias", lname="Refsnes")

• Note: Use ** before the parameter name to receive a dictionary of arguments.

Passing a List as an Argument

• Example:

  def my_function(food):
      for x in food:
          print(x)
  fruits = ["apple", "banana", "cherry"]
  my_function(fruits)

• You can send any data type (string, number, list, dictionary, etc.) to a function, and it will be treated as the same data type inside the function.

Recursion

• Definition: A function that calls itself.

• Example:

  def factorial(x):
      if x == 1:
          return 1
      else:
          return (x * factorial(x-1))
  num = 3
  print("The factorial of", num, "is", factorial(num))

Factorial Calculation Steps

• Diagram of recursive calls:

  • factorial(3) --> 3 * factorial(2)

  • factorial(2) --> 2 * factorial(1)

  • factorial(1) --> returns 1

  • Returns through the levels:

  • Result: 3 * 2 * 1 = 6 .

Factorial Calculations Notation

• Factorial Notation:

  • 4! = 4 * 3!

  • 3! = 3 * 2!

  • 2! = 2 * 1!

  • 1! = 1.