triggers.py

import re
class WordTrigger(Trigger):
    """Sub class of Trigger"""
    def __init__(self,word):
        """Initialization of the WordTrigger class"""
        self.word = word.lower()
    def isWordIn(self,text):
        """Returns whether the object's word's present in the text"""
        #Splits text with punctuations as word separators
        text = re.split('[!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~ ]',text.lower())
        return self.word in text

class TitleTrigger(WordTrigger):
        def evaluate(self,story):
            """Returns whether the object's word's present in the title of the news story"""
            return self.isWordIn(story.getTitle())

class SubjectTrigger(WordTrigger):
        def evaluate(self,story):
            """Returns whether a given word appears in the subject of the news story"""
            return self.isWordIn(story.getSubject())

class SummaryTrigger(WordTrigger):
        def evaluate(self,story):
            """Returns whether a given word appears in the subject of the news story"""
            return self.isWordIn(story.getSummary())
# Composite Triggers

class NotTrigger(Trigger):
    """A composite trigger whose output is opposite to that of the given trigger"""
    def __init__(self,another):
        self.opposite_trigger = another
    def evaluate(self,story):
        return not self.opposite_trigger.evaluate(story)

class AndTrigger(Trigger):
    """A composite trigger which fires if and only the given two triggers evaluate to true"""
    def __init__(self,first_trigger,second_trigger):
        self.first_trigger = first_trigger
        self.second_trigger = second_trigger

    def evaluate(self,story):
        return self.first_trigger.evaluate(story) and self.second_trigger.evaluate(story)

class OrTrigger(Trigger):
    """A composite trigger which triggers if one or both of the given triggers fire"""
    def __init__(self,first_trigger,second_trigger):
        self.first_trigger = first_trigger
        self.second_trigger = second_trigger

    def evaluate(self,story):
        return self.first_trigger.evaluate(story) or self.second_trigger.evaluate(story)