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Lab 10: Using and Designing Classes

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Goals

After the lab, you should be proficient at

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

Deadlines Update

We will have a staggered deadline for this lab:

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: Most Common Names

Recall in Lab 9, we were processing the names of Washington and Lee students. The reason we couldn't easily figure out the most common names is because we couldn't tie the name and the number of occurrences together. We want to sort by number of occurrences, but, given the number of occurrences, we can't look up the name that has that number of occurrences. When we want to package and encapsulate data together, that calls for a new data type.

Objective: Using a class (30)

Open freq.py and read through what the FrequencyPair class represents. What is the data for the class? What is its functionality? Then, check out the test function.

In the Python interpreter, import freq, then run help(freq) so you can see the API.

No, seriously, read through the FrequencyPair class and the test code. How does it work?

Putting it all together. This exercise illustrates how you can use Python to generate graphs. You will use the FrequencyPair class to print out the name frequency results that can be used by another Python program to generate graphs.

Copy lab9.5.py into this directory and name it mostCommonNames.py.

There are two alternatives for leveraging FrequencyPairs to solve the problem:

After you have a list of FrequencyPairs:

  1. Sort the list by the FrequencyPair's count (the default way to sort), following the appropriate example in the FrequencyPair's test function.
  2. Reverse the list so that the objects are in the order of greatest to least
  3. Write the list to a file, one at a time, in the following format: 
    <name> <count>

    For example, an output file for male first names could look like

    James 12
John 9
Robert 7
...

    The data above is not the correct values for the W&L data.

  4. Save your output files for each input file in the data directory. You should name the summary files appropriately, such as female_fnames_freq.dat. (You can name the files either in your program or using Linux commands.) With proper use of functions, you should be able to easily modify the program to handle all four input files at once.

Objective: Generating Graphs

Now, we're going to use a Python program to create bar graphs of the data you generated from your programs using matplotlib, which is useful for generating lots of different kinds of graphs.

Run generateFreqGraphs.py or modify autoGraphExample.py to generate the graphs for each of your data files. If your data files are set up correctly, this should be straightforward.

Show the top 5 results for each data file.

Save the graphs in your data or public_html directory so that the images do not affect your printing later.

Objective: Analysis (5)

In comments at the bottom of your mostCommonNames.py file, analyze the results. The graphs may be helpful or you can look at the output files you generated.

There is no output for this part of the assignment.

Objective: Creating a Social Network

Problem: Create FaceSpace, a program 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

Several Python files are provided for you. Don't start from scratch. Leverage these files, which have contain some code.

Data files for the social network.

Testing (15 pts)

Before we discuss the classes you will implement (below), 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 us 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 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.

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    Natalie Portman                          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 -- Due Tuesday before lab

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 -- Due Tuesday before lab

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.

FaceSpace Driver Program (16) -- Due Tuesday before lab

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.

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. Copy your lab10 directory into your turnin directory.
  2. IDLE and jEdit may create backup files with the "~" extension. Delete these files from your lab directory to save paper when you print.
  3. Make sure you don't have any .png files or 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.

  4. Create the printable lab assignment, using the createPrintableLab command:
    createPrintableLab <labdirname>
  5. View your file using the evince & command.
  6. Print the file using the lpr command.
  7. 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 (125 pts)