Extract words out of a text file

Question

Let's say you have a text file like this one: http://www.gutenberg.org/files/17921/17921-8.txt

Does anyone has a good algorithm, or open-source code, to extract words from a text file? How to get all the words, while avoiding special characters, and keeping things like "it's", etc...

I'm working in Java. Thanks

Answer 1

You could try regex, using a pattern you've made, and run a count the number of times that pattern has been found.

Answer 2

Pseudocode would look like this:

create words, a list of words, by splitting the input by whitespace
for every word, strip out whitespace and punctuation on the left and the right

The python code would be something like this:

words = input.split()
words = [word.strip(PUNCTUATION) for word in words]

where

PUNCTUATION = ",. \n\t\\\"'][#*:"

or any other characters you want to remove.

I believe Java has equivalent functions in the String class: String.split() .

---

Output of running this code on the text you provided in your link:

>>> print words[:100]
['Project', "Gutenberg's", 'Manual', 'of', 'Surgery', 'by', 'Alexis', 
'Thomson', 'and', 'Alexander', 'Miles', 'This', 'eBook', 'is', 'for', 
'the', 'use', 'of', 'anyone', 'anywhere', 'at', 'no', 'cost', 'and', 
'with', 'almost', 'no', 'restrictions', 'whatsoever', 'You', 'may', 
'copy', 'it', 'give', 'it', 'away', 'or', 're-use', 'it', 'under', 
... etc etc.

Answer 3

Basically, you want to match

([A-Za-z])+('([A-Za-z])*)?

right?

Answer 4

This sounds like the right job for regular expressions. Here is some Java code to give you an idea, in case you don't know how to start:

String input = "Input text, with words, punctuation, etc. Well, it's rather short.";
Pattern p = Pattern.compile("[\w']+");
Matcher m = p.matcher(input);

while ( m.find() ) {
    System.out.println(input.substring(m.start(), m.end()));
}

The pattern [\w']+ matches all word characters, and the apostrophe, multiple times. The example string would be printed word-by-word. Have a look at the Java Pattern class documentation to read more.