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# Lesson 304 05 jan14-1500-ay

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### Lesson 304 05 jan14-1500-ay

1. 1. Unit 3: Python Lesson 4: Functions January 5, 2014
2. 2. Lesson 4: Functions Introduction to Programming Lesson 1 Designing a Game Lesson 8 Sorting and Searching Lesson 9 Hardware & Software Lesson 2 Working with Files Lesson 7 Advanced Algorithms Lesson 10 Boolean Logic Lesson 3 Loops Lesson 6 Navigating the Web (?) Lesson 11 Functions Lesson 4 Data Types Lesson 5 Putting It All Together Lesson 12 2
3. 3. Recap from last time (I) • Boolean Logic is a phrase used to describe the way computers think only in TRUE and FALSE • AND, NOT, and OR can be used to combine statements together, but their meanings are a little different from their English meanings • Remember that OR means one, or the other, or both! or Fish only or Chips only Fish and Chips 3
4. 4. Recap from last time (II) • IF statements allow a computer to perform differently when in different situations • Add ELSE to decide what will happen when the IF statement is FALSE • Add ELIF when you have more than two cases to choose from Manchester United wins! Liverpool wins! Penalty kicks 4
5. 5. Functions are important to understand • Computers often use functions to do all kinds of actions, whether it’s adding up numbers or even just showing us text on the screen • To understand how we can program computers to do things for us, we first need to understand more about functions 5
6. 6. A function is like a vending machine • A function is a reusable section of code that performs a specific task • Like a vending machine, a function is programmed to accept something from you (money) and give you something back in return (a fizzy drink) 6
7. 7. Any task can be made into a function (I) • When programming, you can write functions to do just about anything • For example, you could write a function that will accept two numbers and add them together for you Function 7
8. 8. Any task can be made into a function (II) • When programming, you can write functions to do just about anything • For example, you could write a function that will accept two numbers and add them together for you Function • Or you could write a function to accept a calendar date and figure out its day of the week Function 8
9. 9. Functions don’t need to accept anything (I) • Sometimes, functions will perform tasks that don’t require any input from you • For example, you could have a function that adds all the numbers from 1 to 100 and returns the result Function 5050 9
10. 10. Functions don’t need to accept anything (II) • Sometimes, functions will perform tasks that don’t require any input from you • For example, you could have a function that adds all the numbers from 1 to 100 and returns the result Function 5050 • You could even have a function that visits The Telegraph’s website and returns the top headline Function “Drivers face 60mph speed limit on motorways due to EU pollution rules” 10
11. 11. Writing functions in Python is easy! • For a function that will say “Happy Birthday!”, you just need to write: Don’t forget the colon! def birthday(): print “Happy Birthday!” 11
12. 12. Run this function by typing birthday() • For a function that will say “Happy Birthday!”, you just need to write: Don’t forget the colon! def birthday(): print “Happy Birthday!” birthday() • Now that the function is written, every time we run birthday(), , the computer will wish us Happy Birthday! Happy Function Happy Birthday! 12
13. 13. Use words inside the parentheses to give the function an input • We can rewrite our function to say any phrase by adding an input: def parrot(phrase): print phrase Any inputs go here 13
14. 14. Include the input when running the function • We can rewrite our function to say any phrase by adding an input: def parrot(phrase): print phrase Any inputs go here parrot(“Happy New Year!”) , the computer will wish us • Now if we run birthday(), Happy New Year! “Happy New Year!” Function Happy New Year! 14
15. 15. Exercise: Design a Dice Game (I) • For this exercise, we’ll write a function of our own to create a simple dice game in Python • First, open your internet browser, go to labs.codecademy.com, and click on the button for Python 15
16. 16. Exercise: Design a Dice Game (II) • Once the page finishes loading, you should see white space on the left. This is where we’ll be writing the code for our function • The black space on the left is where we’ll run our code to start a game of dice! We’ll start by writing code here We’ll go here later to play dice 16
17. 17. Exercise: Design a Dice Game (III) • On the left side, let’s write the code shown below Don’t forget the colon Remember to tab these lines over 17
18. 18. Exercise: Design a Dice Game (IV) • If you look closely, you’ll see some familiar print statements and an IF statement. Let’s go through this line-by-line 18
19. 19. Exercise: Design a Dice Game (V) Pick a random number from 1 to 6 19
20. 20. Exercise: Design a Dice Game (VI) Pick a random number from 1 to 6 Tell us what we rolled 20
21. 21. Exercise: Design a Dice Game (VII) Pick a random number from 1 to 6 Tell us what we rolled Pick another number from 1 to 6 and tell us what you rolled 21
22. 22. Exercise: Design a Dice Game (VIII) Pick a random number from 1 to 6 Tell us what we rolled Pick another number from 1 to 6 and tell us what you rolled If our roll was larger, tell us we won! 22
23. 23. Exercise: Design a Dice Game (IX) Pick a random number from 1 to 6 Tell us what we rolled Pick another number from 1 to 6 and tell us what you rolled If our roll was larger, tell us we won If your roll was larger, tell us we lost 23
24. 24. Exercise: Design a Dice Game (X) Pick a random number from 1 to 6 Tell us what we rolled Pick another number from 1 to 6 and tell us what you rolled If our roll was larger, tell us we won If your roll was larger, tell us we lost If the rolls were the same, tell us we tied 24
25. 25. Exercise: Design a Dice Game (V) • Now click and wait for a few seconds • Once a second yellow arrow appears on the right side, type to play the game! 25
26. 26. Summary (I) • A function is a reusable section of code that performs a specific task • Think of functions like vending machines – they can accept an input and return an output • Sometimes functions don’t even need an input to return an output Input money Output a fizzy drink 26
27. 27. Summary (II) • The syntax for writing a function in Python looks like this: def parrot(phrase): print phrase Any inputs go here • You run this function by typing its name: parrot(“Happy New Year!”) Happy New Year! 27
28. 28. What to do on your own 1. Go to URL to complete the Codecademy course online 2. Do the practice set on the material learned 1. Take the follow-up quiz to test your understanding 28