# CS 368-4 (2011 Fall) — Day 4 Homework

Due Tuesday, November 8, at the start of class.

## Goal

Write a Python script that reads data from a file, analyzes the data, and prints a report.

Now that we can read files, we can start processing significantly more data than before. Use this new knowledge to read a data file (1.4 MB) containing one English word per line (263536 words), checking for errors of course, and then count the frequency of the words.

Your script will need two values, defined at the top of the script: an input file name, and a threshold (number). Something like this:

```filename = '...'
threshold = 1000```

The input file contains a list of words, one word per line. Your script will read this file, and count the frequency of each of the words. When done, it should then print out all words with a frequency count equal to or greater than the threshold from the command line.

I provide an input file: homework-04.txt for you to experiment with. Your script should run successfully on this file (and ones like it).

The script should be case insensitive — that is, it should treat “the” and “The” as the same word. In Python, use the lower() method on a string to return a copy of the string with all letters in lower case. For example:

```some_text = 'Mixed Case'
print some_text.lower()```

A good threshold number to use is around 1000. Feel free to experiment with numbers higher and lower than that.

Sample output is below. As usual, the exact format of the output does not matter.

```'of': 6568
'with': 1908
'at': 1754
'he': 3128
'a': 6602
'on': 2250
'was': 4220
'and': 6984
'she': 1727
'in': 4747
'from': 1117
'her': 1559
'be': 1294
'that': 2640
'have': 1094
'they': 1101
'for': 2021
'it': 2551
'i': 3342
'as': 1663
'his': 1983
'said': 1430
'the': 15700
'by': 1213
'you': 1147
'were': 1194
'but': 1495
'is': 1180
'to': 6981
'not': 1286```

A key aspect to this assignment is the proper use of Python’s collection types. With proper selection, the problem becomes very straightforward.

Also, the script may be easier to test and debug with the use of a smaller dataset. The dataset provided in “homework-04.txt” is over 250,000 lines. Ultimately, however, once you script works on a small dataset, it should work equally well on the larger dataset. In a Linux or Mac OS X (Terminal) shell, you can create a smaller dataset like this:

`head -n 1000 homework-04.txt > homework-04-small.txt`

Replace the 1000 with the number of lines/words that you want.

## Reminders

Start your script the right way! Here is a suggestion:

```#!/usr/bin/env python

"""Homework for CS 368-4 (2011 Fall)
Assigned on Day 04, 2011-11-03