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Lab 10: Using and Designing Classes

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Goals

After the lab, you should be proficient at

  1. creating and testing your own classes from a specification
  2. developing a larger program (set of classes) to solve a data management problem

Objective: Set Up

  1. Set up the help client:

    run runHelpClient &

  2. Instead of creating a lab10 directory, copy the entire /csdept/courses/cs111/handouts/lab10 directory and all its contents to your cs111 directory.

Review

Review the slides for today's lab.

For this lab, you'll use "real" program names instead of the "lab10.x.py" names we typically use.

Objective: Creating a Social Network

Problem: Create FaceSpace, an application to manage social networks. A social network is a set of users, some of whom are friends. You will keep track of the users and allow users to add friends to their social network.

What is provided

Testing (15 pts)

Before we discuss the classes you will implement (next section), we want to make sure that you know that you need to TEST!

Test your classes before moving on to the user interface. Use the if __name__ == "__main__" code segment that you've used before.

Writing tests helps you isolate problems and debug more easily. If you were to find a problem when you use the user interface, you won't know if there is a problem with your class or with the user interface's use of the class.

Best practices: Implement the constructor and string representation method for each class. Then test them in a test function. Then, implement another method and test it. Continue in this way. This is a little harder for the SocialNetwork class.

If you ask for help and have not sufficiently tested the other methods you already wrote, we will not help until after you have tested and (perhaps) debugged other methods. Your programs are becoming large, more complex, and more difficult to debug if you don't test each part, individually, to make sure that they are all working.

Output

Save the output from executing your test function for each class in an appropriately named file, e.g., person.out

Test Data

I have provided a number of test files for the social network that should be in the data directory of your lab10 directory.

The names of the files are named so that you'll know which is the "people" file and which is the "connections" file. For example, the smallest social network is made up of simple.txt, which contains the people, and simple_connections.txt, which contains the connections.

Summary of Classes

Organization: The classes should be in their own modules. The driver/UI program will import the SocialNetwork class, and the SocialNetwork will import the Person class. Look at the files that you copied for templates.

The following summarizes the classes and their data and functionality. Descriptions for some methods are linked from the summaries.

Person (25)

This class represents an individual in a social network. You'll need to use this class in your other classes. You can add more methods if you want.

Data:

Consider: what should the data types of the data be? We discussed one option in class.

Functionality:

Social Network (54)

The provided template includes the method headers, comments, and placeholders for the method body. The placeholders can be removed after you've implemented the method. An overview of the methods are described below, with links to longer descriptions of the more complex methods.

Data:

Functionality:

The more complex methods are described in more detail below:

String Representation

The string you create should represent the SocialNetwork but does not need to look as "pretty" as the display method, described later. In the given implementation, the string representation contains all the Persons in the social network. (You may want to have some order for the Persons so that it's easier to find them.)

Displaying the Social Network

Display the people in the network in a pretty, sorted-by-id way. For example:

ID      Name                           Num Friends
---------------------------------------------------
0000    Robert Downey Jr                         5
0001    Scarlett Johansson                       5
0002    Henry Cavill                             6
0003    Ben Affleck                              8
0004    Amy Adams                                3
0005    Samuel L. Jackson                        8
0006    Gal Gadot                                8
0007    Chris Hemsworth                          7
0008    Chris Pine                               5
0009    Jaimie Alexander                         9

Adding People to the Network, from a File

See the Lab 10 Slides for the algorithm.

This method will take as input the name of a file and process the file, which contains people that should be added to the social network. (Note that the people do not have friends yet.) To make your code simpler, leverage a method you already wrote.

The format of the file is below:

num_of_users
user_id
name
user_id
name
...

Adding Connections to the Network, from a File

See the Lab 10 Slides for the algorithm.

This method will take as input the name of a file and process the file, which contains the connections between people in the social network. Each line of the file contains two ids and represents the people with those ids are friends.

The format of the file is below:

user_id user_id
user_id user_id
...

Exporting the people to a file

After updating your social network, you may want to save the network to a file so that you can use it later. There are two parts to the network: the people/users and the connections between the people.

This method should write the people in the social network to a file, named by the parameter to this method. The format of the file is as seen above. Essentially, you want to do the opposite of your method that reads in the people from the file.

A good test of this function is to write out the social network (that you did not update) to another file and then check if the files match.

Exporting the connections to a file

This method handles writing the connections to a file. If you're not using the provided template, copy this method from the template. Note the assumptions about the method names.

Adding Exception Handling (5 pts)

Update your SocialNetwork's file-reading methods so that they do exception handling. The methods should perform exception handling and return True iff the file was successfully read. If there was an exception, then print a descriptive error message. We do this for better error handling, since we are creating larger applications, and bad input/errors can cause big problems.

FaceSpace Driver Program (16)

This program maintains a SocialNetwork object and provides an interface for users to manage the social network. If you developed the Person and SocialNetwork classes correctly, the majority of this program should be getting input from the user and calling Person and SocialNetwork methods.

The bulk of the code has been written for you and is in the facespace.py file. If you're having issues with the user interface, make sure that the given program calls the correct methods, as named in your class files.

Part 0: Reading in Your Social Network (3)

Your program should allow the user to enter the names of the people file and the connections file as command-line arguments (see the lab slides). The program should call the appropriate methods to read those files to initialize the social network. If the user does not provide command-line arguments, the program will attempt to read the default files, data/default.txt and data/default_connections.txt.

You must test command-line arguments from the terminal. If you use IDLE, you'll always use the defaults.

For example: python3 facespace.py data/hollywood.txt data/hollywood_connections.txt

Part 1: Interactions with the User (10)

Most of the interactions with the user are implemented for you. You are responsible for implementing the following interactions:

Viewing a person's information:

Which option do you want? v

What is the id of the person you want to view? doej
doej: Jane Doe has 2 friends

Which option do you want? v

What is the id of the person you want to view? a
There is no person with id a

Adding a user and displaying the updated network

Which option do you want? u

What is the id of the user? doej
That user id is already taken.

What is the id of the user? ht8
What is the name of the user? Henry the Eighth

Henry the Eighth has been added to the network.

*************************************
Select one of the following options:
        (D)isplay the social network
        (V)iew a person in the social network
        Add (P)eople to the social network from a file
        Add (C)onnections to the social network from a file
        Add a (U)ser to the social network
        Add a pair of (F)riends to the social network
        E(X)port the social network
        (Q)uit the program
Which option do you want? d

ID     Name                 Num Friends
----------------------------------------
01     John Doe                       2    
02     Jane Smith                     2         
03     James Jones                    2         
ht8    Henry the Eighth               0

Part 2: Storing the Social Network Before Quitting (3)

Before exiting the program when the user selects the quit option, you should save the social network to the files specified on the command-line/the default files, as appropriate.

Output from FaceSpace

Run FaceSpace in Idle3 (which means that it will not test your use of command-line arguments--I will test that functionality) and save the output, as usual, in an appropriately named file. Make sure you demonstrate the error handling abilities of your code. This is your grand finale! Show me what you got!

Extra Credit

Additional Functionality (up to 12 pts)

We discussed as a class some additional functionality that your classes may have. After you have completed the required functionality, you can add more functionality. (Which class should implement this functionality?) Some of your suggestions included

Finishing up: What to turn in for this lab

  1. When you, as a pair, are ready to submit OR if you are at the end of the lab period, run pairturnin.sh labx partnerusername
    where labx is the name of the lab you are submitting and partnerusername is your partner's username on the lab machines (the person whose account you are not using to write the code). For more information about the command, see the wiki.

    If you want to copy your pairs' work into your cs111 directory--either just to have it or to work on your code on your own--use the script startup.sh. Run this command from the account that you want For example, run startup.sh labx partnerusername
    where labx is the name of the lab you're working on and partnerusername is your partner's username on the lab machines.

    For more info, see the wiki.

  2. If you complete the lab on your own after the lab period, submit your lab into your turnin directory.
  3. IDLE and jEdit may create backup files with the "~" extension. Delete these files from your lab directory to save paper when you print.
  4. Make sure you don't have any data files (i.e., outputs from the common names or exported people files) in the lab10 directory. Those files should be in your data directory.

    Perform the following steps from your cs111 directory.

    Note that each command below links to a page with more information about using the command.

  5. Create the printable lab assignment, using the createPrintableLab command:
    createPrintableLab <labdirname>
  6. View your file using the evince command.
  7. Print the file using the lpr command.
  8. Log out of your machine when you are done.

Labs are due at the beginning of Friday's class. You should hand in the printed copy at the beginning of class, and the electronic version should be in the turnin directory before 2:20 p.m. on Friday.

Ask well before the deadline if you need help turning in your assignment!

Grading (115 pts)