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Prepare for next time No need to buy the book – Free online at http://www.nltk.org/bookhttp://www.nltk.org/book Read Chapter 1 – http://nltk.googlecode.com/svn/trunk/doc/book/ch01.html http://nltk.googlecode.com/svn/trunk/doc/book/ch01.html Install NLTK (see next slide) – Warning: It might not be easy (and it might not be your fault) – Let us know how it goes (both positive and negative responses are more appreciated)

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Installing NLTK http://nltk.googlecode.com/svn/trunk/doc/book/ch01.html http://nltk.googlecode.com/svn/trunk/doc/book/ch01.html Chapter 01: pp. 1 - 4 – Python – NLTK – Data

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Homework

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George Miller’s Example: Erode Exercise: Use “erode” in a sentence: – My family erodes a lot. to eat into or away; destroy by slow consumption or disintegration – Battery acid had eroded the engine. – Inflation erodes the value of our money. Miller’s Conclusion: – Dictionary examples are more helpful than defs Definition Examples George Miller: Chomsky’s Mentor & Wordnet

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Introduction to Programming Traditional (Start with Definitions) Constants: 1 Variables: x Objects: – lists, strings, arrays, matrices Expressions: 1+x Statements: Side Effects – print 1+x; Conditionals: – If (x<=1) return 1; Iteration: for loops Functions Recursion Streams Non-Traditional (Start with Examples) Recursion def fact(x): if(x <= 1): return 1 else: return x * fact(x-1) Streams: – Unix Pipes Briefly mentioned – Everything else

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Python def fact(x): if(x <= 1): return 1 else: return x * fact(x-1) def fact2(x): result=1 for i in range(x): result *=(i+1); return result Exercise: Fibonacci in Python Recursion Iteration

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Lists

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Strings

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Subscripting

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Python Objects Lists >>> sent1 ['Call', 'me', 'Ishmael', '.'] >>> type(sent1) >>> sent1[0] 'Call' >>> sent1[1:len(sent1)] ['me', 'Ishmael', '.'] Strings >>> sent1[0] 'Call' >>> type(sent1[0]) >>> sent1[0][0] 'C' >>> sent1[0][1:len(sent1[0])] 'all' First Rest

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Flatten: Inverse of Split >>> def flatten(list): if(len(list) == 1): return list[0]; else: return list[0] + ' ' + flatten(list[1:len(list)]); First Rest flatten = split -1

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Types & Tokens Polymorphism

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Polymorphism (From Wikipedia)

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Flatten: Inverse of Split >>> def flatten(list): if(len(list) == 1): return list[0]; else: return list[0] + ' ' + flatten(list[1:len(list)]); +

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