Lecture05

Knowledge Representationin

Digital HumanitiesAntonio Jiménez Mavillard

Department of Modern Languages and LiteraturesWestern University

Lecture 5

Knowledge Representation in Digital HumanitiesAntonio Jiménez Mavillard

* Contents: 1. Why this lecture? 2. Discussion 3. Chapter 5 4. Assignment 5. Bibliography

2

Why this lecture?


* This lecture... · goes deeply into the development of programming skills · introduces strings as means of text represention, the study subject for the rest of the course

3

Last assignment discussion


* Time to... · consolidate ideas and concepts dealt in the readings · discuss issues arised in the specific solutions to the projects

4

Chapter 5

Text Representation in Python

1. More programming Python2. Complex data types

Knowledge Representation in Digital HumanitiesAntonio Jiménez Mavillard5

Chapter 5

1 More programming in Python 1.1 Functions 1.2 Basic data types


Chapter 5

2 Complex data types 2.1 Strings


More programming in Python


Functions

* Debugging · Syntax errors + colon at the end of def + indentation inside def · Logic errors + infinite recursion


Functions

* Definition · A funcion is a named sequence of statements that performs a task · To use a function: 1. Define it 2. Call it


Functions

* Definition · Syntax: + Definition

def function_name(parameters): #definition statements #body


Functions

* Definition · Syntax: + Call

function_name(arguments)


Functions

* Arguments vs parameters · The arguments are values passed to the function call · The arguments are assigned to the parameters


Functions

* Arguments vs parameters · Example:


#print versiondef mean(x, y): print (x + y) / 2

In [1]: from mean1 import mean

In [2]: mean(2, 4)3

In [3]:

Functions* Arguments vs parameters · Example: + The parameter x takes the value of the first argument, 2 + The parameter y takes the value of the second argument, 4 + The function calculates (2 + 4) / 2 and prints the result


Functions

* Scope · A block is a section of code, consisting of one or more statements grouped together · Examples: branches in if statements, code in loops for and while, body of functions...


Functions* Scope · Variables created in a function are local to the function and do not exist outside · Two ways to communicate with the exterior: + arguments (input) + return statement (output)


Functions

* Scope · Example:


#return versiondef mean(x, y): return (x + y) / 2


In [2]: m = mean(2, 4)3

In [3]: m


In [5]: m = mean(2, 4)

In [6]: mOut[6]: 3

In [7]:

#print versiondef mean(x, y): print (x + y) / 2

Functions

* Exercise 1 · An integer y is a divisor of the integer x if the reminder of the division x/y is equals to 0 · An integer number is prime if it is greater than 1 and has no divisors other than 1 and itself


Functions

* Exercise 1 · Write a function that prints the list of prime numbers less than 100


Functions

* Exercise 1 (solution)


#prime numbersdef prime_list(n): i = 1 while i <= n: if is_prime(i): print i i = i + 1

Functions



def is_prime(n): result = True i = 1 while i <= n: if is_divisor(i, n) and i != 1 and i != n: result = False break i = i + 1 return result

Functions



def is_divisor(x, y): return y % x == 0

Functions* Exercise 1 (solution)


In [1]: from prime import prime_list

In [2]: prime_list(20)1235711131719

In [3]:

Functions

* About functions · There exist predefined functions ready to be used · Programmers can define new functions · A function can call another functions


Functions

* Why functions? · Functions are reusable so they make a program shorter by eliminating repetitive code · Long programs divided into functions are easier to write, read, understand and debug


References

Downey, Allen. “Chapter 3: Functions.” Think Python. Sebastopol, CA: O’Reilly, 2012. Print.


Basic data types

* Debugging · Logic errors + mistake a variable data type


Basic data types

* int · Type for numbers · Examples: 1, 1234567890* long · Type for long numbers · Examples: 101000 (a one followed by a thousand zeros)


Basic data types

* float · Type for floating-point numbers · Examples: 1.0, 3.1416* bool · Type for logic values · Examples: True, False


Basic data types

* The type function · Returns the type of a value, variable or expression


In [1]: type(1)Out[1]: int

In [2]: x = 10**1000 + 1

In [3]: type(x)Out[3]: long

In [4]:

Basic data types

* The type function · Returns the type of a value, variable or expression


In [4]: y = 3.1 + 2.21

In [5]: type(y)Out[5]: float

In [6]: type(x == y)Out[6]: bool

In [7]:

Basic data types

* Type conversion functions · int: converts to int (if possible)


In [1]: int("123")Out[1]: 123

In [2]: int(3.1416)Out[2]: 3

In [3]:

Basic data types

* Type conversion functions · float: converts to float (if possible)


In [1]: float(123)Out[1]: 123.0

In [2]: float('3.1416')Out[2]: 3.1416

In [3]:

Basic data types

* Type conversion functions · bool: converts to bool (if possible)


In [1]: bool([1, 2, 3])Out[1]: True

In [2]: bool(0)Out[2]: False

In [3]:

Basic data types

* Type conversion functions · str: converts to str (if possible)


In [1]: str(123)Out[1]: '123'

In [2]: str(not True)Out[2]: 'False'

In [3]:

References

“5. Built-in Types — Python v2.7.6 Documentation.” N. p., n.d. Web. 17 Feb. 2014.


Complex data types


Strings

* Debugging · Syntax errors + not closing ''/“” · Semantic errors + not accessing the first and/or last element


Strings

* Debugging · Logic errors + modifing an element + accessing to a non-existing element - index out of range


Strings

* str · Type for strings · Examples: 'hello world!', “hello world!” · A string is a sequence of characters · Suitable to represent texts


Strings

* Indices · Three ways to access a string: + As a whole - Example: word + Its characters one at a time - Syntax: string[index] - Example: word[1]


Strings

* Indices · Three ways to access a string: + Slices - Syntax: string[index_1:index_2] - Example: word[2:5]


Strings

* Exercise 2 · Figure out the range of indices for a string · Try out several examples · Extract a general pattern for any string


Strings* Exercise 2 (solution)


In [1]: s = 'digital'

In [2]: s[1]Out[2]: 'i'

In [3]: s[0]Out[3]: 'd'

In [4]: s[7]IndexError: string index out of range

In [5]: s[6]Out[5]: 'l'

In [6]:

Strings* Exercise 2 (solution)


In [6]: s = 'humanities'

In [7]: s[1]Out[7]: 'u'

In [8]: s[0]Out[8]: 'h'

In [9]: s[10]IndexError: string index out of range

In [10]: s[9]Out[10]: 's'

In [11]:

Strings

* Exercise 2 (solution) From 0 to the string's number of characters minus 1


Strings* Indices word = 'digital'


d i g i t a l

0 1 2 3 4 5 6

In [1]: word = 'digital'

In [2]: wordOut[2]: 'digital'

In [3]: word[1]Out[3]: 'i'

In [4]: word[2:5]Out[4]: 'git'

Strings

* Inmutability · Strings are inmutable (cannot be modified) · To modify a string, it is necessary to reasign changes to a new (or same) string


Strings

* Inmutability · Example: word += 's' + Equivalent to word = word + 's' + Accesses the value of the variable word, concatenates an s, and reasign the result to the variable word again


Strings

* Some functions and operators · The len function returns the number of characters in a string


In [1]: len('digital')Out[1]: 7

In [2]:

Strings

* Exercise 3 · Write a function that receives a string and returns the number of characters (do not use the len function and do use a for loop)


Strings



def count(s): counter = 0 for c in s: counter += 1 return counter

Strings

* Exercise 4 · What does this function do?


def any_function(string, char): result = 1 index = 0 while index < len(string): if string[index] == char: result = index break index += 1 return result

Strings

* Exercise 4 (solution) It returns the (first) index of a character in a string or -1 if the not found


Strings

* Exercise 5 · Write a function that counts the number of ocurrences of a character in a string


Strings



def count(s, ch): counter = 0 for c in s: if c == ch: counter += 1 return counter

Strings* Some functions and operators · The operator in checks if a string is contained in another string


In [1]: s = 'abcde'

In [2]: 'bc' in sOut[2]: True

In [3]: 'rs' in sOut[3]: False

In [4]:

References

Downey, Allen. “Chapter 8: Strings.” Think Python. Sebastopol, CA: O’Reilly, 2012. Print.


Assignment

* Assignment 5: Lexicon · Readings + Word play (Think Python) + Files (Think Python)


Assignment* Assignment 5: Lexicon · Project + Grady Ward, as part of the Moby lexicon project, has collected a list of 113,809 official crosswords; that is, words that are considered valid in crossword puzzles and other word games


Assignment

* Assignment 5: Lexicon · Project + Download a copy of the word list from http://thinkpython.com/code/words.txt


http://thinkpython.com/code/words.txt

Assignment

* Assignment 5: Lexicon · Project + Many words in English have endings (suffix) that identifies them as nouns + Some of these suffixes common to nouns are (non-exhaustive list):


Assignment

* Assignment 5: Lexicon · Project -age, -ance, -ant, -cy, -dom, -ee, -ence, -ent, -er, -hood, -ing, -ism, -ist, -ity, -ment, -ness, -or, -ry, -ship, -sion, -tion, -tude


Assignment* Assignment 5: Lexicon · Project + Write a program that reads the file words.txt and: - prints all the nouns (according to the previous list) - prints the number of nouns - prints the number of total words


Assignment* Assignment 5: Lexicon · Project + Write a program that reads the file words.txt and: - calculates and prints the proportion (expressed in % with decimals) of nouns with respect to the total words


References

Downey, Allen. “Chapter 14: Files.” Think Python. Sebastopol, CA: O’Reilly, 2012. Print.

Downey, Allen. “Chapter 9: Case Study - Word Play.” Think Python. Sebastopol, CA: O’Reilly, 2012. Print.

“Moby Project.” Wikipedia, the free encyclopedia 19 Jan. 2014. Wikipedia. Web. 20 Feb. 2014.


Bibliography

“5. Built-in Types — Python v2.7.6 Documentation.” N. p., n.d. Web. 17 Feb. 2014.

Downey, Allen. Think Python. Sebastopol, CA: O’Reilly, 2012. Print.

“Moby Project.” Wikipedia, the free encyclopedia 19 Jan. 2014. Wikipedia. Web. 20 Feb. 2014.


Lecture05

Technology

Transcript of Lecture05