MIT 6.00x - PSet 6 answers by jonrsharpe

ProblemSet6.py

# 1. NewsStory
class NewsStory(object):

    def __init__(self, guid, title, subject, summary, link):
        self.guid = guid
        self.title = title
        self.subject = subject
        self.summary = summary
        self.link = link
        
    def getGuid(self):
        return self.guid
    
    def getTitle(self):
        return self.title

    def getSubject(self):
        return self.subject

    def getSummary(self):
        return self.summary
    
    def getLink(self):
        return self.link


# 2. a) WordTrigger
class WordTrigger(Trigger):

    def __init__(self, word):
        self.word = word
        
    def isWordIn(self, text):
        text = [a.strip(string.punctuation).lower() for a in text.split(" ")]
        for word in text:
            if self.word.lower() in word.split("'"):
                return True
        return False
        

class TitleTrigger(WordTrigger):

    def evaluate(self, story):
        return self.isWordIn(story.getTitle())
        

class SubjectTrigger(WordTrigger):

    def evaluate(self, story):
        return self.isWordIn(story.getSubject())


class SummaryTrigger(WordTrigger):

    def evaluate(self, story):
        return self.isWordIn(story.getSummary())


# 2. b) Composite Triggers
class NotTrigger(Trigger):

    def __init__(self, t1):
        self.t1 = t1

    def evaluate(self, story):
        return not self.t1.evaluate(story)


class AndTrigger(Trigger):

    def __init__(self, t1, t2):
        self.t1 = t1
        self.t2 = t2

    def evaluate(self, story):
        return self.t1.evaluate(story) and self.t2.evaluate(story)

        
class OrTrigger(Trigger):

    def __init__(self, t1, t2):
        self.t1 = t1
        self.t2 = t2

    def evaluate(self, story):
        return self.t1.evaluate(story) or self.t2.evaluate(story)


# 2. c) PhraseTrigger
class PhraseTrigger(Trigger):

    def __init__(self, phrase):
        self.phrase = phrase

    def isPhraseIn(self,text):
        return self.phrase in text

    def evaluate(self, story):
        if self.isPhraseIn(story.getTitle()):
            return True
        if self.isPhraseIn(story.getSummary()):
            return True
        if self.isPhraseIn(story.getSubject()):
            return True
        return False

# 3. Filtering
def filterStories(stories, triggerlist):
    output = []
    for story in stories:
        for trigger in triggerlist:
            if trigger.evaluate(story):
                output.append(story)
                break
    return output

# 4. Making triggers
def makeTrigger(triggerMap, triggerType, params, name):
    if triggerType == 'TITLE':
        newTrigger = TitleTrigger(params[0])
    elif triggerType == 'SUBJECT':
        newTrigger = SubjectTrigger(params[0])
    elif triggerType == 'SUMMARY':
        newTrigger = SummaryTrigger(params[0])
    elif triggerType == 'PHRASE':
        newTrigger = PhraseTrigger(" ".join(params[0]))
    elif triggerType == 'NOT':
        newTrigger = NotTrigger(triggerMap[params[0]])
    elif triggerType == 'AND':
        newTrigger = AndTrigger(triggerMap[params[0]], triggerMap[params[1]])
    elif triggerType == 'OR':
        newTrigger = OrTrigger(triggerMap[params[0]], triggerMap[params[1]])
    else:
        raise ValueError
    triggerMap[name] = newTrigger

Just a small bug: In the "PHRASE" elif statement in "#4. Making triggers," you run str.join() on params[0] with the " " separator, but that just ends up joining each character in params[0] with a space in between. The problem specification asks you to join all of the words in the "params" list with a space in between. To fix, just omit the [0] and you'll be running str.join() on the list rather than the first word in the list. So the two lines would now be:

elif triggerType == 'PHRASE':
newTrigger = PhraseTrigger(" ".join(params[0]))