Updated Week 06 and 07 Functions In Python.pptx

function

1. Functions In Python

2. Learning Objectives Explain how to define and write functions Illustrate how to call functions Analyze how to pass different arguments to functions Demonstrate how to return a value from functions Computer Science Department, UET Lahore.

3. Working Example Write a Python Program to calculate the mean of five numbers input by user. Formula for calculating the mean is: For Example: Computer Science Department, UET Lahore. Input: 1, 2, 3, 4 Output: 2.5 Mean = {Sum of numbers} ÷ {Total numbers}

4. Working Example: Solution Computer Science Department, UET Lahore. add = 0 for x in range(0,5,1) : num = int (input(“Enter Number: ”)) add = add + num print (“Mean: ”, add/5 ) Output: Enter Number: 1 Enter Number: 2 Enter Number: 3 Enter Number: 4 Enter Number: 5 Mean: 3.0 To calculate the mean, We can use this method

5. Is there any better Solution? Computer Science Department, UET Lahore. add = 0 for x in range(0,5,1) : num = int (input(“Enter Number: ”)) add = add + num print (“Mean: ”, add/5 ) Output: Enter Number: 1 Enter Number: 2 Enter Number: 3 Enter Number: 4 Enter Number: 5 Mean: 3.0 To calculate the mean, We can use this method

6. Is there any better Solution? Computer Science Department, UET Lahore. Better solution in terms of readability and simplicity . Yes, there is. But before moving to the solution lets take a real life example of Automobile factory .

7. Automobiles in Factory How do the automobiles are created in the factory? Computer Science Department, UET Lahore.

8. Components of Automobiles Wheels, Brakes, Engine, Steering Wheels etc are the components of the car. Computer Science Department, UET Lahore.

9. Automobiles in Factory Wheels, Brakes, Engine, Steering Wheels are manufactured separately and they are assembled in the automobile factory. Computer Science Department, UET Lahore.

10. Functions Functions are like short programs that can take input, process on it, and may return the results Functions are like building blocks . They let you divide complicated programs into manageable pieces Computer Science Department, UET Lahore.

11. Functions: How to Create? Functions are defined using “ def ” keyword in python. Parameters are inputs to the function and they are separated by commas. “ return ” is the keyword for returning the output Example: Computer Science Department, UET Lahore.

12. Functions: How to Call? Functions are called by writing the name of the function and passing the parameters to the functions. Output of the function is received in a new variable. Example: Computer Science Department, UET Lahore.

13. Functions : Previous Example Computer Science Department, UET Lahore. Let’s Use Functions to solve the same problem.

14. Functions : Previous Example Computer Science Department, UET Lahore. def calculate_sum (): add = 0 for x in range (0,5,1): num = int ( input ("Enter Number: ")) add = add + num return add To calculate the sum , We can use this function def calculate_avg ( sum ): avg = sum/5 return avg To calculate the average, We can use this method sum = calculate_sum () print ("Mean: ", calculate_avg (sum) ) The rest of program would look like this .

15. User-Defined Functions: These Functions are called user-defined functions because they are defined by the users. For the program’s simplicity and more readability, users can define as many functions as they want. Computer Science Department, UET Lahore.

16. User-Defined Functions: Benefits Functions make the code reusable . We can declare them once and use them multiple times. Functions make the program easier as each small task is divided into a function. Functions increase readability . Computer Science Department, UET Lahore.

17. Two-types of Functions: User-Defined Functions Pre-Defined (Library) Functions Computer Science Department, UET Lahore.

18. Pre-Defined (Library) Functions: Library functions are the built-in functions in Python programming. Programmers can use library functions by invoking the functions directly ; they don't need to write the functions themselves. Computer Science Department, UET Lahore.

19. Functions : Previous Example Computer Science Department, UET Lahore. Instead of writing this complete code , Python library (statistics) has already written this code.

20. Pre-Defined Functions : Extended Computer Science Department, UET Lahore. import statistics my_list = [] for x in range (0,5,1): y = int ( input ("Enter Number: ")) my_list.append (y) mean = float ( statistics.mean ( my_list ) ) print("Mean: ", mean ) Output: Enter Number: 1 Enter Number: 2 Enter Number: 3 Enter Number: 4 Enter Number: 5 Mean: 3.0 To calculate the mean, We can use Pre-defined Functions Don’t Worry. We will learn about Lists in Coming Lectures.

21. Built-in Functions: Python Standard library Computer Science Department, UET Lahore.

22. Built-in Functions: with importing math library Computer Science Department, UET Lahore. import maths

23. Built-in Functions: with importing math library Computer Science Department, UET Lahore. For Example:

24. Learning Objective In this lecture, we learnt about functions , how to define functions with different parameters, differentiate between built-in and user-defined functions. Computer Science Department, UET Lahore.

25. Conclusion A function is a block of organized, reusable code that is used to perform a single, related action. Functions are of 2 types Built-in Functions User-defined Functions Functions can have zero or more parameters. Syntax to define and call Functions is as follows: Computer Science Department, UET Lahore.

26. Take Home Tasks 1. Create a function that takes the age in years and returns the age in days. Note: Use 365 days as the length of a year for this challenge. Ignore leap years and days between last birthday and now. Expect only positive integer inputs. Examples: calcAge(65) ➞ 23725 calcAge(0) ➞ 0 calcAge(20) ➞ 7300 Computer Science Department, UET Lahore.