Yr 9 a computer science

1. Yr 9 a computer science Nice to meet you variable challenge! 1.Variable assessment Looping in python 2.Looping assessment Drawing in python using turtle

2. Last session we covered binary and hexadecimal Today we are going to spend majority of time coding completing assessments

3. Objectives To understand how to use variables To create a program with a variable Complete a loop using python: a while loop,a for loop and a

4. Program 1-nice to meet you print("Please type your name in") my_name = input () print("Nice to meet you "+ my_name) **if using python 3.2 then do not use raw_input use input instead** Make sure that you save your program as My_name.py Run your program once saved by pressing f5

5. Make sure When you run your program that you put your name in speech marks! Otherwise it wont work!!

6. Program 2-extension print("Please type your name in") my_name = input () print("Nice to meet you " + my_name) print("So, " + my_name + ", what is your favourite food?") favourite_food = input () print("Ah, your favourite food is " + favourite_food) Once typed in save , the run by pressing f5 You will need to save this as questions .py

7. Variable assessment for 3 lines of extra code you get 3 points For 2 lines of extra code you get 2 points For 1 line of extra code you get 1 point See who can be the coding champion

8. Extension task Consider adding more complex questions into the script. Notice in the 4th line above it is necessary to have two + signs, one either side of the variable my_name. Nb :Common errors to watch for are not having a complete pair of double quotation marks or adding + signs between variables and strings.

9. Looping in python

10. Loops strings and tuples-loopy string program This program takes a word from the user and prints its letters in order on separate lines This program provides a good example of a for loop Type this code in then save as loopy_string.py Then press f5 and run

11. Loopy Program explained The new idea in this program is the for loop Ie: For letter in word: Print letter Explain the code:All sequences are made up of elements A string is a sequence in which each element is one character In the case of the string loop , the first element is the character “l” …. A for loop marches over or iterates over a sequence one element at a time A for loop uses a variable that gets each successive element of the sequence In my loop the ,letter is the variable that gets each successive character of “loop”. Inside the loop body the loop can then do something with each successive element In the loop body ,I simply print LETTER

12. Looping-while loops Computers can be programmed to continue repeating code while a condition is True. Look at the example below for an idea name = "" while name != "Batman": print("Somebody call Batman!") print("Are you him? ") name = input("What's your name?") As you can see in the example in the left, the code will keeping looping and asking the same question while the answer is not Batman. Notice the nesting of statements underneath the while? It is the indented code that will keep looping

13. Task 1 Write a while loop to ask someone what the best football team in the world is. Repeat the question until they say the correct team.

14. Harder loops! Now we will try to write one more while loop this time using a condition. Again this task is a lot harder. Look at the example below and try to write your own. secret_number = 6 guesses = 3 while guesses > 0: print("Can you guess what number I am thinking?) guess = int(input("write a number ")) if guess == secret_number: print("Well done, you guessed correctly!") break else: guesses = guesses ­1 if guesses == 0: print("You have no guesses left!") In this code, we also learn of the break statement. This will tell the PC to skip to the next line of code that is not in the current indented nesting.

15. Loops harder still The code below shows an example of how to add a list of numbers together: count = 5 number = 0 print("this programme will work out the total of a list of numbers") while count > 0: number = number + int(input(print("Please enter a number :"))) count = count ­ 1 print(number)

16. Loop assessment 1

17. Using turtle module in python

18. Agent P, I have been hearing some rumours about a Python Turtle. Please find it and invite it to join O.W.A.C.A.! Aims: For students to gain some experience with Python's turtle module. Objectives: ALL: Use the turtle module in the interpreter. MOST: Experiment with simple drawings using turtle. SOME: Make simple programs using the turtle module and explore some of its more advanced features.

19. Have a go at using these basic commands. First we create an instance of the Turtle class. I called it 'a', you can call it what you like. Then we can use the dot notation to invoke the turtle's methods. a.fd(n) -> go forward n pixels. a.lt(n) -> turn left n degrees. a.color(n) -> change the color of the line. a.home() -> go back to 0,0. a.pensize(n) -> change the width of the line. a.up() -> take the pen off the paper.

20. Have a play with the turtle object. Can you work out how to ... ? -> turn right -> go back -> put the pen down again Mini Tasks In the interpreter: -> draw a triangle -> draw a pentagon -> draw a circle (don't use the built-in method). If you have used Scratch, the turtle module may seem familiar to you. They are both descended from the LOGO programming language.

21. You can use the “goto” method to move the turtle to a position on the screen by its co-ordinates. The center of the turtle's window is 0,0. You can write words in the turtle window. You can also change the turtle to a turtle shape and stamp an imprint on the screen. If you type the name of your turtle object and a dot, IDLE will show you a list of methods that you could invoke. Have a play and find out what some of them do.

22. If you succeeded with the triangle and pentagon scripts, you probably noticed that you could generalise the procedure. And a circle is just a polygon with very many sides ....

23. I asked the program to draw a polygon with 360 sides, all of length 1. Task: For the next activity, we need a function that will draw a quarter of a circle. See if you can work this out for yourself. If you can, I want something that will draw this shape. It is just two quarter-circles facing one another.

24. Turtle Challenge Once you have the “petal” shape function, you should be able to write a program that draws flowers like this. Choose some nice colours and vary the number of “petals” in the flower until you find a design that you like.

25. Only if you are stuck ... Here's a possible quarter-circle function. circumference = π * 2 * radius We are going to draw the arc in steps corresponding to one degree. Let's call the length of these “step”. step = (π * 2 * radius) / 360 step = 0.01745 ... For my version, I decided that 0.02 was close enough.

26. Using fill Just use begin_fill() before you start drawing the shape you want to fill. Then, use end_fill() and the shape will be filled for you.

27. Task: Have a play with that filled square routine. If you alter the amount of turn you can write a function that produces results similar to these. You'll probably want to use a while loop. How will your program know when it is time to stop?