Lab 1, CSC 101

Welcome to CSC/CPE 101. This first lab will help you to familiarize yourself with the programming environment provided in the department labs. This is the environment in which you will be working all quarter long, so take this time to ask questions and to get comfortable with the lab setup.


The lab machines run a distribution of the Linux operating system. For simplicity, and to gain experience in a, potentially, new environment, we will do our coursework in this environment.


Open a terminal window. To do so, from the system menu on the desktop toolbar, select ApplicationsSystem ToolsTerminal. The Terminal program will present a window with a command-line prompt. At this prompt you can type Linux commands to list files, move files, create directories, etc. For this lab you will use only a few commands. Additional commands can be found from a link on the course website.

In the terminal, type ls at the prompt and hit <Enter>. This command will list the files in the current directory. (In some environments, e.g., Windows, a directory is commonly referred to as a folder.) If you type pwd, the current directory will be printed (it is often helpful to type pwd while you are navigating directories). If you type tree, then you will see a tree-like listing of the directory structure rooted at the current directory.

Create a new directory for your coursework by typing mkdir cpe101. Use ls again to see that the new directory has been created.

Change into this new directory with cd by typing cd cpe101. To move back "up" one directory, type cd ...

To summarize

Though these basic commands are enough to continue with this lab assignment, you should consider working through a Unix tutorial (many can be found on the web) at a later time.

Executing a Program

Download the file. Place this file in the cpe101 directory created above; this can be done via the browser (by selecting the location to save to), via the graphical file manager, or through the use of the mv command in the terminal window (e.g., from the cpe101 directory, after downloading, type mv ~/Downloads/ .). If you need assistance doing this, please ask.

Unpack this file by typing unzip at the command prompt. This will create a directory named lab1; change into this directory by typing cd lab1. If you now list the contents of the lab1 directory, you should see the following files: In addition, you will find the following subdirectories: line vehicle.

A Python program is written in a plain text file. The program can be run by using a Python interpreter.

You can see the contents of by typing more at the prompt.

To execute the program, type python at the command-line prompt.

To summarize


There are many options for editing a Python program. On the department machines, you will find vi, emacs/xemacs, nano, gedit, and some others. The editor that one uses is often a matter of taste. You are not required to use a specific editor, but we will offer some advice (and we will try to help with whichever one you choose).

If you decide to connect to the department machines from home, then you'll want an editor that can work via a remote connection without much effort (i.e., without installing and running additional software). This makes gedit a less than desirable candidate (unless you want to learn two editors). The others will work fine, though you'll see some differences between xemacs and emacs (which is what you'd use remotely).

vi and emacs are powerful editors once you have learned how to use them. But they require some initial effort to learn their command sequences. Knowledge of one of these will, however, serve you well for quite some time.

nano (or pico, when nano isn't available) is very simple. It will feel, in some respects, like using Notepad. It is quick to learn and easy to use. Some people will mock others for using nano (some people are elitist dorks). You might choose to start with nano and then switch to one of the other editors as you "outgrow" nano (the others provide features that can aid you when programming).

A note concerning tabs: Whichever editor you choose, you should lookup how to convert tabs to spaces so that your Python source files do not contain a mix of tabs and spaces (or avoid tabs altogether).

In general, whichever editor you choose, you should invest some time early to learn how to navigate quickly within a file. More specifically, you will want to learn how to jump to a specific line, to search within the file, and copy/paste lines.

If you cannot decide, then use nano. You always have the option of switching at a later time.

You will start the editor by typing the name at the prompt followed by the name of the file that you wish to edit. For instance, nano -Ec (note the -Ec is useful to 1) convert tabs to spaces (E) and 2) direct nano to display the line number for the cursor's current position(c)).

To Do: Using your editor of choice, modify to replace World with your name and fill out the header comment at the beginning of the file. Execute the program to see the effect of this change.

Interactive Interpreter

The Python interpreter can be used in an interactive mode. In this mode, you will be able to type a statement and immediately see the result of its execution. Interactive mode is very useful for experimenting with the language and for testing small pieces of code, but your general development process with be editing and executing a file as discussed previously.

Start the interpreter in interactive mode by typing python at the command prompt. You should now see something like the following.

Python 2.6.6 (r266:84292, Jan 22 2014, 09:42:36)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.

The >>> is the interpreter's prompt. You can type an expression at the prompt to see what it evaluates to. Type each of the following (hit enter after each one) to see the result. When you are finished, you can exit the interpreter by typing ctrl-D (i.e., hold the control key and hit d).

Test Cases

Many people tend to focus on writing code as the singular activity of a programmer, but testing is one of the most important tasks that one can perform while programming. Proper testing provides a degree of confidence in your solution. During testing you will likely discover and then fix bugs (i.e., debug). Writing high quality test cases can greatly simplify the tasks of both finding and fixing bugs and, as such, will actually save you time during development.

For this part of the lab you will practice writing some simple test cases to gain experience with the unittest framework. Using your editor of choice, open the file. This file defines, using code that we will treat as a boilerplate for now, a testing class with a single testing function.

In the test_expressions function you will see a single test case already provided. You must add additional test cases to verify that the following expressions (exactly as written) produce the values that you expect. Note that you will want to use assertAlmostEqual instead of assertEqual to check computations that are expected to result in a floating point value.

Run the program by typing python You should now see a report of any tests that did not succeed.

Compound Data -- Classes and Objects

In this part of the lab you will write new code. You are asked to complete the definition of two classes.

The following steps will walk you through writing the class definition and test cases for the first class. You will then repeat the process for an additional class. Pay careful attention to each of these steps as you will repeat them throughout the quarter.

Line class

In the line subdirectory, perform each of the following steps.


In the line subdirectory, create a file named This is referred to as a "source" file. In this file you will provide the definition of the line class.

Create a class named Line. Within this class you will define the __init__ function (note that there are two underscore characters before init and two after) to take, in this order, self, x1, y1, x2, and y2 as arguments. This function must initialize the corresponding fields in self with the values of x1, y1, x2, and y2.


In the provided file, edit the test_line function to create a Line (with values for the x1, y1, x2, and y2 arguments of your choice) and then test that each field was properly initialized.

Write a second test case by adding a test_line_again function to create and verify a second Line.

You will also need to add import line to the top of this file. Try it out. If you cannot get it working, ask for assistance.

Type python to run the test cases.

vehicle class

As you did for Line, provide a class definition and test cases for a Vehicle in the vehicle directory. A Vehicle value must keep track of the number of wheels, the amount of fuel remaining, the number of doors, and whether or not the vehicle has a roof. Give some thought to the types of values that you will use for each of these attributes.

In, write the test cases for a Vehicle to verify that each field is properly initialized.


Demonstrate lab1_test_cases, the line/line_tests, and the vehicle/vehicle_tests programs to your instructor to have this lab recorded as completed. In addition, be prepared to show your instructor the source code for your line and vehicle programs.


This step will introduce the tool that you will use to submit assignments.

The handin command will vary by section.

This command will submit your files to the appropriate assignment repository (e.g., 101lab1) for the specified instructor account.

Note that, in general, you can resubmit your files as often as you'd like prior to the posted deadlines. Each subsequent submission will replace files of the same name.

You can use handin without specifying files to check what you submitted (e.g., handin akeen 101lab1) and without specifying a submission directory to list available directories (e.g., handin akeen).


All done? Great. Consider using any remaining time by working through a Unix tutorial. This is a good time to get more familiar with the environment and with your editor.