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CS 100 Introduction to Computing

CS 100 Introduction to Computing. Introduction to JES. Developed by Mark Guzdial, Georgia Institute of Technology, 2003–2004; modified by Robert H. Sloan & Pat Troy, University of Illinois at Chicago, 2005, for educational use. Installation. Installing JES and starting it up Windows users:

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CS 100 Introduction to Computing

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  1. CS 100Introduction to Computing Introduction to JES Developed by Mark Guzdial, Georgia Institute of Technology, 2003–2004; modified by Robert H. Sloan & Pat Troy, University of Illinois at Chicago, 2005, for educational use.

  2. Installation • Installing JES and starting it up • Windows users: • Just copy the folder from the CD • Double-click JES application • Mac OS X users: • Just drag (i.e., copy) JES from Mac folder into your Applications • Double-click JES application • Enter a blank in the form for turnin (we probably won’t use) • There is always the Help Menu (Take a look at it) • Lots and lots of excellent help

  3. We will program in JES • JES: Jython Environment for Students • A simple editor (for entering in our programs): We’ll call that the program area • A command area for entering in commands for Python to execute.

  4. JES - Jython Environment for Students

  5. Tour of JES • Save and Save As • Cut/Copy/Paste with shortcut keys • Turnin • TA will give instructions for submitting your Jython • This will start with Lab 10; they’re in the lab • Help • Explain is contextualized help: Highlight a JES (media) function • Lots of help on mediatools and the like

  6. Python understands commands • We can name data with “=” (assignment operator) • We can print values, expressions, anything with print

  7. Using “print” in JES >>> print 34 + 56 90 >>> print 34.1/46.5 0.7333333333333334 >>> print 22 * 33 726 >>> print 14 - 15 -1 >>> print ”Hi" Hello >>> print ”Hi" + ”Bob!" HiBob!

  8. Command Area Editing • Up/down arrows walk through command history • You can edit the line at the bottom • Just put the cursor at the end of the line before hitting Return/Enter.

  9. Demonstrating JES for files and sounds >>> print pickAFile() /Users/guzdial/mediasources/barbara.jpg >>> print makePicture(pickAFile()) Picture, filename /Users/guzdial/mediasources/barbara.jpg height 294 width 222 >>> print pickAFile() /Users/guzdial/mediasources/hello.wav >>> print makeSound(pickAFile()) Sound of length 54757 >>> print play(makeSound(pickAFile())) None >>> myfilename = pickAFile() >>> print myfilename /Users/guzdial/mediasources/barbara.jpg >>> mypicture = makePicture(myfilename) >>> print mypicture Picture, filename /Users/guzdial/mediasources/barbara.jpg height 294 width 222 >>> show(mypicture)

  10. Writing a recipe: Making our own functions • To make a function, use the command def • Then, the name of the function, and the names of the input values between parentheses (“(input1)”) • End the line with a colon (“:”) • The body of the recipe is indented (Hint: Use two spaces) • That’s called a block

  11. Making functions the easy way • Get something working by typing commands • Enter the def command. • Copy-paste the right commands up into the recipe

  12. A recipe for playing picked sound files def pickAndPlay(): myfile = pickAFile() mysound = makeSound(myfile) play(mysound) Note:myfile and mysound, inside pickAndPlay(), are completely different from the same names in the command area.

  13. Blocking is indicated for you in JES • Statements that are indented the same, are in the same block. • Statements that are in the same block as where the line where the cursor is are enclosed in a blue box.

  14. A function for playing picked picture files def pickAndShow(): myfile = pickAFile() mypict = makePicture(myfile) show(mypict)

  15. The Most Common JES Bug:Forgetting to Load • Your function does NOT exist for JES until you load it • Before you load it, the program is just a bunch of characters. • Loading encodes it as an executable function • Save and Save As • You must Save before Loading • You must Load before you can use your function

  16. What if you forget your variable names? showVars()

  17. JES - Help Menu • The help menu is very very useful. Before you start, make sure you take a look at Getting Started with JES and Programming in Jython.

  18. MOST IMPORTANT THING TO DO TO PASS THIS CLASS! • DO THE EXAMPLES! • Try them out for yourself. Try to replicate them. Understand them • EVERY WEEK, TYPE IN AT LEAST TWO OF THE EXAMPLES FROM CLASS and/or THE TEXTBOOK • To understand a program means that you know why each line is there. • You will encounter all the simple-but-confusing errors early—BEFORE you are rushing to get homework done!!

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