Computer Science 15-110, Spring 2011
Class Notes:  File IO Practice


This code requires that you download words.txt and place it on your Desktop.


# File IO Practice

#########################################################
# File IO code from course website
#########################################################

import os

def getDesktopPath(filename = ""):
    # next line is odd, but works in Windows/Mac/Linux
    homepath = os.getenv('USERPROFILE') or os.getenv('HOME')
    return homepath + os.sep + "Desktop" + os.sep + filename

def fileExists(filename):
    return os.path.exists(filename)
  
def deleteFile(filename):
    if (fileExists(filename) == True):
        os.remove(filename)

def readTextFile(filename):
    if (fileExists(filename) == False):
        print "File does not exist:", filename
        return None
    fileHandler = open(filename, "rt")
    text = fileHandler.read()
    fileHandler.close()
    return text

def readTextFileAsList(filename):
    # readlines includes '\n' characters, so we'll use split() instead
    text = readTextFile(filename)
    if (text == None):
        return None
    return text.split("\n")

def writeTextFile(text, filename):
  fileHandler = open(filename, "wt")
  fileHandler.write(text)
  fileHandler.close()

#########################################################
# Basic dictionary lookup
#########################################################

def testDictionary():
    wordList = readTextFileAsList(getDesktopPath("words.txt"))
    done = False
    while (not done):
        prompt = "Enter a word to lookup (or just <enter> to quit): "
        word = raw_input(prompt)
        lookupWord = word.lower()  # dictionary is all-lowercase
        if (word == ""):
            done = True
        elif (lookupWord in wordList):
            print word, "is in the dictionary!"
        else:
            print word, "is NOT in the dictionary!!!"
    print "bye!"

testDictionary()   

#########################################################
# LevenshteinEditDistance
# From http://code.activestate.com/recipes/572156-bk-tree/
# Reqiured for spell checker (below)
#########################################################

def levenshteinEditDistance(s1, s2):   
    if s1 == s2: return 0
    if len(s1) > len(s2):
        s1,s2 = s2,s1
    r1 = range(len(s2) + 1)
    r2 = [0] * len(r1)
    i = 0
    for c1 in s1:
        r2[0] = i + 1
        j = 0
        for c2 in s2:
            if c1 == c2:
                r2[j+1] = r1[j]
            else:
                a1 = r2[j]
                a2 = r1[j]
                a3 = r1[j+1]
                if a1 > a2:
                    if a2 > a3:
                        r2[j+1] = 1 + a3
                    else:
                        r2[j+1] = 1 + a2
                else:
                    if a1 > a3:
                        r2[j+1] = 1 + a3
                    else:
                        r2[j+1] = 1 + a1
            j += 1
        aux = r1; r1 = r2; r2 = aux
        i += 1
    return r1[-1]

import time

def spellCheck(targetWord, wordList):
    time0 = time.clock()
    closestList = []
    closestDistance = levenshteinEditDistance(targetWord, wordList[0])
    for word in wordList:
        if (abs(len(word) - len(targetWord)) <= 1): # make this 2 or 3 for more matches
            distance = levenshteinEditDistance(targetWord, word)
            if (distance == closestDistance):
                closestList += [word]
            elif (distance < closestDistance):
                closestDistance = distance
                closestList = [word]
    time1 = time.clock()
    print "time: ", (time1 - time0)
    return closestList
   
def testSpellChecker():
    wordList = readTextFileAsList(getDesktopPath("words.txt"))
    done = False
    while (not done):
        prompt = "Enter a word to lookup (or just <enter> to quit): "
        word = raw_input(prompt)
        lookupWord = word.lower()  # dictionary is all-lowercase
        if (word == ""):
            done = True
        elif (lookupWord in wordList):
            print word, "is in the dictionary!"
        else:
            print word, "is NOT in the dictionary!!!"
            print "nearest words:", spellCheck(lookupWord, wordList)
    print "bye!"

testSpellChecker()