CSC 101: Lab Manual#11 Programming Turtle Graphics in Python Lab due date: 5:00pm, day after lab session

Transcription

1 CSC 101: Lab Manual#11 Programming Turtle Graphics in Python Lab due date: 5:00pm, day after lab session Purpose: The purpose of this lab is to get a little introduction to the process of computer programming in a high-level language - the process that software professionals use to write a program. In particular, you will be exposed to the syntax of the Python programming language and us a set of tools called Turtle Graphics. Lab Instructions Step 0) a) Create a folder for Lab11 b) Download each of the files linked from the lab web site. (For each, right-click and choose "Save As ") Store each of these files in your Lab11 folder. c) Create a new Word document and save it as Screenshots.doc into the Lab11 folder. As you work through this manual, - Answer all labeled questions on the Lab 11 report handout. - Insert all screenshots into the Word document in the order requested. How to make a screenshot? Use Snip of PrtScr. If you need a refresher, look back at past labs (eg lab5 on Boolean logic) Step 1) Be certain that you have a correct version of Python as outlined in the PreLab. If you are not certain, ask the instructor or one of the TAs to help you double-check. For this lab, you may wish to refer to the Turtle Graphics Reading that was part of the pre-lab. Step 2) Open Idle like you did in the prelab. This window is called the Shell or the Interpreter. Step 3) Open the file "LabProg1.py" via the "File" menu, and the "Open" command.

2 You should see something like this image. This window is the program window or the code window. Now, run the program. HOW? Under the "Run" menu, choose "Run Module". The program draws a box. Try to understand why the program does what it did. If you do not understand, ask questions of the instructor or the TAs. Question 1: How many pixels wide is the box? How many pixels high is the box? - Go to the SECOND line that says: turtle.forward(100) Remove the last parenthesis: turtle.foward(100 This causes what is called a syntax error. Run the program again. ( Run menu, Run Module ) (Now, and throughout this lab, click "OK" when it asks you to save.) Question 2: What happened when you ran the program this time? Be sure to describe ANYthing that Put the parenthesis back. Now, on that line, delete the 100, so that the line looks like: turtle.forward() Recall from the prelab reading that 100 is an argument. Run the program. Question 3: What happened when you ran the program this time? Be sure to describe ANYthing that Question 4: Why do think it is important for there to be an argument to the turtle.forward function? Question 5: What are two turtle graphics functions that take no arguments? NOW, change the line to say: Run the program again. turtle.forward(100,200) Question 6: What happened when you ran the program this time? Be sure to describe ANYthing that Question 7: Does the behavior in Question 6 make sense? Why or why not? NOW, change the line back to its original state : turtle.forward(100) Run the program again to make sure that it has been restored to its original functionality.

3 Change the program to have the turtle draw a box that is much wider (at least 300 pixels wide), but the same height. SCREENSHOT 1: Take a screenshot of the code that you modified. SCREENSHOT 2: Take a screenshot of the turtle window (and hence your wider box). You may now close LabProg1.py. Step 4) Open the file "LabProg2.py" via the "File" menu, and the "Open" command. Run this program. Question 8: What does this program do? Notice three lines of code that say turtle.color From these lines, we see that Python knows the colors "Black", "white" and "red" by name. Make changes to the program and run it to determine the answer to the following: Question 9: Which of the following colors does Python know about by name: Yellow Magenta Rose Pink LightBlue Gray Cyan Grey Chartreuse Now, change the turtle.color commands to use RGB. "viewport". Create a blue "camera", a black "lens", and a white Question 10: Using RGB, what command did you give to make each of the following colors: a) blue b) black c) white Question 11: a) Now, change the "camera" to be purple using RGB, by turning on all of the red and all of the blue (but leaving green off). What was the command you used? b) Now, turn down the red and the blue (but still leave the green off). Does the color get darker or lighter? Near the top of the program, we see lines for "xariables" named x, y, width, and height. These allow the code below to be more flexible. Change the x = -200 line to say x = -300 Question 12: Run the program now. What happens? Spend some time and play with the values of x, y, width, and height. See what the program does differently for each one. Question 13: Does the camera move and scale correctly for any value of x,y, width, and height you put in? If not, say what values you used to get it to break.

4 Set values for x, y, width, and height to have the camera appear at the lower right corner of the window, with a reasonable proportion. Screenshot 3: take a screenshot of the code window that shows your values of the variables Screenshot 4: take a screenshot of the camera appearing in the lower right corner. You may now close LabProg2py. Step 5) Open the file "LabProg3.py" via the "File" menu, and the "Open" command. Run the program. Discover that it does NOTHING. This may seem surprising, given that there is a lot of code in the window. This is because almost all of the code is in functions, which are sets of code that CAN do things, but do not unless they are called. At the bottom of the file, type drawground() drawsky() Run the program and watch what happens. Now, change the code to say: drawsky() drawground() Question 14: What happens differently when you run this changed program? Now, add the code: drawflower(0,50,20,"red") Run the program and observe what happens. Change the arguments to be 200, 100, 40, and yellow Run the program and observe what changes. Now, modify the program so that it has four flowers. Flower1: right hand side of the screen, 70 pixels high, red flower of size 40 Flower2: left hand side of the screen, 140 pixels high, yellow flower of size 70 (Use RGB for this one). Flower3: center of the screen, 80 pixels high, purple flower of size 30 Flower4: between flower1 and flower3, taller than the other flowers, white blossom smaller than the other flowers Question 15: What line of code did you use for each of the flowers? Step 6) Open the file "LabProg4.py" via the "File" menu, and the "Open" command. Run this program. See that it creates a spiral. At the bottom of the file is the function call, with four arguments. Change one of the arguments and run the program again. See what changes. Change another argument and run the program again. See what changes. Etc. In other words, futz with the arguments till you understand what each of them does. Now, add a SECOND call to the spiral function (with different parameters). Observe how the spirals interact. TASK: Create a pretty picture using the spirals. Your picture must include at least two spirals, but may include more.

5 Screenshot 5: Take a screenshot of your code for calling the spirals (the bottom of the code file) Screenshot 6: Take a screenshot of your spirals. HANDIN: Upload your Screenshots.doc file to Sakai. Hand in your written answers on the report.