CMSI 3630: Welcome to Week 01

WELCOME!!

Today, the first day of the semester, will be a pretty typical 'first day of class'. We'll cover the course syllabus, then take a brief tour of the course website so you'll know where to find your project, reading, and homework assignment information.

If time remains, the rest of the class [or the second class meeting for the two-a-week section] we will begin to look at some of the fundamental concepts of database systems and the associated theory.

The Grand Tour

First things first:

A little welcome message…

First we need to cover the basics, since fundamentals are critical to success in anything!

Helpful Links and Programming Information

There are many many many many many books and links that can help you with Python programming. A few of these are listed here. I've tried to get some of the better ones, 'better' meaning 'more complete' in terms of texplanations and examples. As I uncover more good ones, I'll be adding them to the list, so check back several times during the semester to see what new things have been added.

And don't worry, you won't be responsible for knowing anything particular about the sites, only the information about Python Programming.

Tools you will use during the semester

Initial roll call and other sundries

And now for the dreaded pariah of all classes, the tell-the-professor-all-about-me excercise, which is guaranteed to have you all shifting uneasily in your seats! So, tell me a little about yourself, including:

Assignment Submissions

All homework assignments will be done individually, unless group work is preferred. We will determine which way on the first day of class. You are free to collaborate in discussing the concepts, but you must submit your own work, either individually or as a group. If submitting as a group, only one copy needs to be submitted. I will be comparing to make sure, and I'm wise to things like simply changing variable names and so on……

Assignments are mixed, with exercises consisting of both programming projects and short answer questions. As many of you may have heard, I'm a big believer in fostering critical thinking skills, so there will be questions that are intended to make you think about what you are doing in various respects like morals, ethics, and decomposition of problem statements as well as just breaking the problems into smaller parts to solve them.

All homework will be submitted in GitHub. Please get an account if you don't already have one, and make a repository for this class. Please be sure that I am a collaborator on your repository so that I can clone it and can upload evaluations to it. Also, make your repository private so that no one but you and I can see anything of its contents.

Please name your repository CMSI-3630_<your-last-name>. I have automated scripts set up for evaluating your work that expect this naming convention. If you change that convention you will break my scripts. You should also have a directory [folder] hierarchy in your repo that looks like the following structure:

  1. classwork
    1. classwork01
    2. classwork02
    3. classwork03
    4. classwork04
    5. classwork05
    6. classwork06
    7. [etc...]
    8. classwork14
  2. homework
    1. homework01
    2. homework02
    3. homework03
    4. homework04

I will be using this folder structure to perform the evaluations of your work. I use the GitHub desktop on my Windows machine to duplicate your repo locally for doing those evaluations, and I have several scripts that I set up to facilitate compiling and running your programs and projects. Any deviations from the above structure means my scripts will not work with your submissions, so you will NOT get credit. IF YOU NEED HELP GETTING THIS SET UP, PLEASE ASK ME, ONE OF YOUR CLASSMATES, OR ONE OF THE TA'S [teaching assistants] IN THE KECK LAB DOOLAN 112 to assist you.

Additionally, CODE THAT DOES NOT COMPILE WILL NOT BE EVALUATED. PERIOD. The time for submitting code with compile errors is past. In a very few cases, if there is some really small error that I could fix with a single edit, I had a nominal policy of correcting those errors if there were only one or two obvious ones. Any more than that, though, and I will NOT be doing that, so it's best to make sure your code compiles/runs before you turn it in.

REMEMBER: I use the command line for compiling and running. If you are using an Integrated Development Environment [IDE] like IDLE, be sure your program can be successfully run from the command line. It's an extra step for some of you, yes, but this reflects the real world of software development – just because it works for you in IDLE doesn't mean that the USERS who run your code will be running it from IDLE, if they even HAVE IDLE. Most of your users will think IDLE is that thing your car does before you step on the gas.

Java vs. JavaScript vs. Python

OK, let's state the obvious up front: JAVA IS NOT JAVASCRIPT. If you had me for CMSI 185 or CMSI 186 [or anything else] you should realize this already. Professor Forney has a little saying on his website: Java is to JavaScript as Car is to Carpet. …or something like that.

What's Your Interpretation?

The point is, despite the similarity in the names, they are two very different animals. JavaScript is an interpreted language, which means that the computer [actually the JavaScript interpreter that is RUNNING on the computer] interprets each line of JavaScript code, one-at-a-time, turning it into the executable code [bit patterns] that the machine can actually execute. The same thing goes for Python ~ interprested language, meaning there is an engine of some sort that actually runs your code.

On the other hand, Java is a compiled language, which means you have to run a software tool called a compiler on your source code to translate it BEFORE you can run it.

Actually, it's even a bit more complicated than that, because the Java compiler translates the source code into what is known as byte code, which is not really runnable on the hardware processor of your computer either. Instead, there is a program called the Java Virtual Machine, or JVM, which is sort of like a layer on top of the operating system of your computer that will run the Java byte code. It is the JVM that interprets the byte code into what the computer CPU/GPU can actually execute. Most of the time, you don't care about this, and your USERS certainly won't give a fig. But it IS an important distinction…

We'll see this again in a week or so.

So, in Java We Need a Type-righter…… [facepalm]

Apart from being compiled vs. interpreted, Java is a statically-typed language, while JavaScript and Python are dynamically-typed languages. This means that in JavaScript or in Python, you can define a variable horse that has the string Trigger in it, then three lines later you can set the value of horse to be 37, and the JavaScript or the Python interpreter will happily handle that for you. However, with Java, you must define horse to have a specific data type, like String, and it will forever after [in THAT program] be of the String data type – you can never put a number in it, because it will be an error.

Something that the languages have in common, although they implement things differently, is the idea of OBJECTS. An object is essentially a user-defined, complex data type. We'll see more of THAT later, too.

Examples:

   # Python code, dynamically typed
   myString = "This is a string in the Python Language."
   primeNumber = 23                       # this is a 'number' data type in JavaScript
   myAmount = 234.56                      # this is ALSO a 'number' data type
   myString = 23                          # this is NOT an error!! [Dynamic typing]

Start up your Python interpreter and enter the above code to see what happens!

   // JavaScript code, dynamically typed
   var myString = "This is also a string in the JavaScript Language.";
   var primeNumber = 23;                  // this is a 'number' data type in JavaScript
   var myAmount = 234.56;                 // this is ALSO a 'number' data type
   myString = 23;                         // this is NOT an error!! [Dynamic typing]

Enter the above JavaScript code in the Script Runner to see what happens there.

   // Java code, statically typed
   class Tester {
      String myString = "This is also a string in the Java Language.";
      int primeNumber = 23;                  // this is a 'primitive' data type, an 'integer'
      double myAmount = 234.56;              // this is a 'primitive' data type, a double-precision number
      myString = 23;                         // this is an ERROR!!  [Static typing]
   }

Try typing the Java code into a file, then compile it [or check your editor marks] to see the error. You can also try typing it into the Python Tio.run page to see what happens there. [TIO stands for Try It Online ~ a pretty cool tool!]

Beginning Python

So, since we are going to *USE* Python…

So that all the sections of this class can get the same introduction to the Python Language [as well as to Data Structures in general], Dr. Toal, our LMU resident programming language 'mystic chef and guru' has put together several REALLY GOOD web pages to introduce the Java language. I have, with his express permission, modified those pages for use with Python, and we'll be using those pages for the first few weeks of this course to augment our learning experience. Here is the first one, called Python Workshop!

OK then, what is a CLASS? [Encapsulation]

So, within that context, a CLASS is a user-defined data type, which can be used as a sort of template to make objects of that class. It is a named collection of things that can hold data, and things that can operate on that data.

There is really a LOT more to it than this, but for brevity's sake I'm reducing it to the bare bones

The fact that classes define data and the behaviors that can operate on that data leads to the idea of encapsulation, also known as data hiding. The basic idea is that the programmer defines the data in the class, and then also defines the operations for that data, which allows her to have complete control over how that data is accessed. If everything is private to the class, only the methods within that class may access the data directly; any other object will have to call some method [a gettor or settor] to access the data.

Here is an example in Java, properly annotated so you can see what it looks like in a statically typed language:

  /**
   * A simple Java Class file example
   * @author Professor Johnson
   * @version 1.0.0
   */
   public class Sample {
      private String myString = "This is a string in the Java Language.";
      private int primeNumber = 23;          // 'primitive' data type, an 'integer'
      public  double myAmount = 234.56;      // 'primitive' data type, a double-precision number

     /**
      * Constructor
      * @param value String to set in the myString field
      */
      public Sample( String value) {
         myString = new String( value );
      }

     /**
      * Method to reset the "myAmount" field value
      * @param newAmount double precision value to set the field to
      * @return the integer value that is the reset amount
      */
      public double resetAmount( double newAmount ) {
         myAmount = newAmount;
         return myAmount;
      }

     /**
      * Method to determine if a number is prime
      * @param value an integer which is potentially a prime number
      * @return boolean value, true if the value passed is prime, false if not
      */
      public boolean isPrime( int value ) {
         boolean result = false;
         // some code that determines prime-ity
         return result;
      }
   }

And here is the same thing in Python:

   class Sample:
      myString = "This is a string in the Python Language."
      primenumber = 23
      myAmount = 234.56

      def __init__( self, value ):        # this is the 'constructor
         self.myString = value

      def resetAmount( newAmount ):
         myAmount = newAmount
         return myAmount

      def isPrime( value ):
         result = False
         # some code to determine prime-ness of 'value'
         return result

      # this is how we instantiate the class
      s1 = Sample( "New string")
      s2 = Sample( "Another new string")

      # this is how we can access the values
      print( s1.myString )
      print( s1.primenumber )
      print( s2.myAmount )

In-class Assignment #1

This assignment is to make sure you have your environment working, so you are ready for the rest of the semester. It is perfectly OK to ask your classmates for assistance if you get stuck and I am busy helping someone else.

You will need to do the following to produce your first program for this session:

  1. Install Python on your computer if you haven't already done so; you can get it from the Python main download page. I use the latest, Python 3.11.1 [at this writing]
  2. Install a text editor or IDE on your computer if you haven't already done so; this is optional, since Python comes with a quasi-IDE called IDLE that you can use easily
  3. Create a bookmark in your favorite browser to the some of the Python links provided on the week One page if you haven't already done so
  4. Make sure you have a directory structure somewhere on your hard drive that mimics your github repo structure for this course; you can always set it up in github, then clone it to your local machine
  5. Create a file called sayHello.py in a the classwork01 directory on your local drive.
  6. Using your text editor that you installed or use the IDLE GUI to edit the file and create a program that will simply print Hello, World! to the console using the print() function.
  7. Run your program to make sure everything works.
  8. Now add to your program to prompt the user to input her name from the console using the Python input() function
  9. Modify your program to change the Hello, World! message to say Hello, followed by the name that the user has input. For example, if the user enters Dorothy, your program should output Hello, Dorothy! Don't forget to add the exclamation point at the end!
  10. Run your program to make sure everything works.
  11. Test your program with several different inputs, like dog, $237.19, and just pressing Enter without entering anything. See if you can break your program, and if you can, figure out why it broke and see if you can fix it. If you CAN'T break it, see if you can figure out why it's so robust which is the term for a program that will handle [nearly] everything gracefully.
  12. Go to GitHub and set up your repo and submission structure if you haven't already done so.
  13. Upload and commit your completed SayHello.py file to your repo
  14. Pat yourself on the back for a job well done! [Just don't hurt yourself…]

NOW FOR PART TWO ~ Our First Algorithm!!

Homework Assignment #1

I know this isn't due for a while, but i wanted to give you a heads-up on the homework assignments that you will be doing this semester. They are all available from the syllabus page, but just to make sure …

Week One Wrap-up

That's probably enough for the first week. Be sure to check out the links to the related materials that are listed on the class links page. Also, don't forget the project page!


I hear, and I forget.
I see, and I remember.
I do, and I understand.
— Ancient Chinese Proverb