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Assignment 4 Concordance.
1 Concordance (an application of hash tables)
This assignment has several parts: implementing different versions of the hash table from the text (with some
additional functionality) and writing an application that builds a concordance. A Webster’s dictionary
definition of concordance is: “an alphabetical list of the main words in a work.” In addition to the main words,
your program will keep track of all the line numbers where these main words occur.
Word and Line Concordance Application
The goal of this assignment is to process a textual data file to generate a word concordance with line numbers
for each main word. A dictionary ADT is perfect to store the word concordance with the word being the
dictionary key and a list of its line numbers being the associated value for the key. Since the concordance
should only keep track of the “main” words, there will be a second file containing words to ignore, namely a
stop-words file (stop_words.txt). The stop-words file will contain a list of stop words (e.g., “a”, “the”, etc.) —
these words will not be included in the concordance even if they do appear in the data file. You should not
include strings that represent numbers. E.g. “24” or “2.4” should not appear.
The following is an example and the output file.
The general algorithm for the word-concordance program is:
1) Read the stop_words.txt file into your implementation of a hashtable containing only stop words.
Make sure to check the number of stop words so that you can size the dictionary appropriately! (WARNING:
Make sure you do not include the newline character (‘\n’) when adding the stop words.)
2) Process the input file one line at a time to build the word-concordance dictionary. This dictionary should
contain the non-stop words as the keys. Associated with each key is its value where the value consists of a list
containing the line numbers where the key appears. DO NOT INCLUDE DUPLICATE LINE NUMBERS.
3) Generate a text file containing the concordance words printed out in alphabetical order along with their
line numbers. One word per line. See the sample output files.
It is strongly suggested that the logic for reading words and assigning line numbers to them be developed and
tested separately from other aspects of the program. This could be accomplished by reading a sample file and
printing out the words recognized with their corresponding line numbers without any other word processing.
Assignment 4 Concordance.docx 2 February 14, 2022
Collision resolution:
• Your implementation should use Open Addressing using quadratic probing for collision resolution.
• Note that you will not have to incorporate deleting items from your hash table
Your basic hash function should take a string containing 1 or more characters and return an integer. Use
Horner’s rule to compute the hash efficiently.
Also, your hash table size should have the capability to grow if the input file is large. After insertion of an item, if
the load factor exceeds 0.5, you should grow the hash table size.
Start with a default hash table size of 191, then if increases are necessary, use:
“new table size” = 2 *“old table size” + 1 (use this “new table size” even if it is no longer a prime)
DATA FILES –
• the stop words in the file stop_words.txt
• six sample data files that can be used for preliminary testing of your programs:
– file1.txt, file1_sol.txt – contains no punctuation to be removed
– file2.txt, file2_sol.txt – contains punctuation to be removed
– declaration.txt, declaration_sol.txt – larger file for test
Your code for creating the concordance will be contained in two files: hash_quad.py and concordance.py
The hash_quad.py file will contain the HashTable class and the methods described for that class.
Each entry in the hash table will consist of a string (a word) and list of line numbers in which the word appears. How
you implement an “entry” is your design choice. You could use a Python tuple for each entry with the first element
as the key (word) and the second element as the value (list of line numbers), for example:
(“cat”, [1, 3, 8])
Another possibility would be to define a class for an entry that has key and value attributes.
The following starter files (containing the methods that you must implement) are available in Canvas.
Do not change the names of the classes, methods, or attributes specified in the starter files.
• hash_quad.py
• concordance.py
SUBMISSION
Four files:
─ hash_quad.py: containing class HashTable with all of the specified methods, using quadratic probing for
collision resolution
─ hash_quad_tests.py – tests for the HashTable methods specified by the assignment o This file should
contain tests only for the functions specified above and should only test functionality required by the
specification. These tests must run properly on a valid instructor solution and will be tested to see if they can
catch bugs in incorrect solutions.
─ concordance.py: containing class Concordance with all of the specified methods
─ concordance_tests.py – tests for the Concordance methods specified by the assignment o This file should
contain tests only for the functions specified above and should only test functionality required by the
specification. These tests must run properly on a valid instructor solution and will be tested to see if they can
catch bugs in incorrect solutions.
Helpful resources:
• A “How to on sorting in Python”: https://docs.python.org/3/howto/sorting.html . You may use the built-in
sorting routines in Python so you may find this reference helpful.
• Python has some built in capability to eliminate punctuation that you may find helpful. See string.constants
https://docs.python.org/3.1/library/string.html (apostrophes should be removed, hyphens should be replaced by
a space – other punctuation can be removed or replaced by a space)

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