NLTK & PythonDay 8

LING 681.02Computational Linguistics

Harry HowardTulane University

11-Sept-2009 LING 681.02, Prof. Howard, Tulane University

2

Course organization

NLTK should be installed on the computers in this room!

NLPP §2 Accessing text

corpora and lexical resources

§2.2 Conditional frequency

11-Sept-2009 LING 681.02, Prof. Howard, Tulane University

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Practice

Do "Your Turn" up to p. 55Exercises 2.8.2-4, 2.8.8

NLPP §2 Accessing text

corpora and lexical resources

§2.3 More Python: Reusing code

11-Sept-2009 LING 681.02, Prof. Howard, Tulane University

6

Creating a program with a text editor

Create the monty.py program.

11-Sept-2009 LING 681.02, Prof. Howard, Tulane University

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Other IDEs

Eclipse (Java Dev) + Pydev pluginhttp://www.eclipse.org/downloads/

Mac users should use Cocoa version

http://pydev.org/index.html

Xcode Tools now supports PythonIt is part of optional installation on DVD.You have to register as a developer to

download it from http://developer.apple.com/

11-Sept-2009 LING 681.02, Prof. Howard, Tulane University

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Functions

What might you want to put in your program? Why, a function, of course!

A function takes an input to produce an output or return value:>>> def my_function_name(my_inputs)... # calculate my_output... return my_output...

11-Sept-2009 LING 681.02, Prof. Howard, Tulane University

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Modules and higher

As you accumulate functions, you will want to store them somewhere.Save them all in the same text file with the .py

suffix, i.e. my_mod.py, called a module and import them as needed:

from my_mod import my_function_name

Hierarchyfunction < module < package < library

NLPP §2 Accessing text

corpora and lexical resources

§2.4 Lexical resources

11-Sept-2009 LING 681.02, Prof. Howard, Tulane University

11

Lexical resources

What is a lexicon?a collection of words and/or phrases,

sometimes with additional information such as part of speech or meaning

What is a lexical entry?A headword/lemma, along with that other info

saw1 [verb] past tense of see

saw2 [noun] cutting instrument

11-Sept-2009 LING 681.02, Prof. Howard, Tulane University

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More corpora

Wordlist corporawordsNames CorpusDo ex. 2.8.8

CMU Pronouncing DictionaryDo ex. 2.8.12

Comparative wordlistsSwadesh wordlistShoebox/Toolbox

NLPP §2 Accessing text

corpora and lexical resources§2.5 WordNet

11-Sept-2009 LING 681.02, Prof. Howard, Tulane University

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Semantic relations

SynonymSynonyms are grouped into synsets in

WordNetlook at codeDo Your turn

Next time

Q/P2

Do two of Ex. 2.8.16-19

Start NLPP §3