# keep 3 lines around any line containing "cat", ie the line above, the line and the line below
# separate one triple of lines from the next by a line with "---", and put one "---" at the top and bottom of the list
# write "found 17 cats" on the last line of the destination file, where 17 is the number of lines you found containing cat
# use 
#      line with possible cat".find("cat") >= 0
# to detect a feline presence

def showCatsNeighbourhood(src, dst):
    s, d = open(src, 'r'), open(dst, 'w')
    l1 = s.readline()
    occurs = 0
    if len(l1) > 0 :
        d.write("---\n")
        l2 = s.readline()
        if len(l2) > 0 :
            l3 = s.readline()
            keepGoing = True
            while keepGoing :
                if l2.find("cat") >= 0 :
                    d.write(l1)
                    d.write(l2)
                    d.write(l3)
                    d.write("---\n")
                    occurs = occurs + 1
                if len(l3) > 0 :
                    keepGoing = True
                else :
                    keepGoing = False
                l1 = l2
                l2 = l3
                l3 = s.readline()
    d.write("found "+str(occurs)+" cats\n")
    s.close(); d.close()
    
    
# write a class which takes a word and a synonym, and puts it in a dictionary if it is not there already, otherwise it adds it to the list of synonyms, but it doesn't store duplicates.

class Thesaurus :
    def __init__(self) :
        self.dict = {}
    def add(self,word,synonym) :
        if word in self.dict :
            self.dict[word].add(synonym)
        else :
            self.dict[word] = set([synonym])
    def lookup(self,word) :
        if word in self.dict :
            print("The synonyms of "+word+" are")
            idx = 1
            for syn in self.dict[word] :
                print("  "+str(idx)+".  "+syn)
                idx = idx + 1
        else :
            print("There are no synonyms of "+word+".")    
            
class FamilyTree :
    def __init__(self,name,father,mother) :
        self.name = name
        self.father = father
        self.mother = mother
    def printTree(self,prefix) :
        print(prefix + self.name)
        if type(self.father) == type("cat") :
            print(prefix + "father: "+self.father)
        else : 
            print(prefix + "father: ")
            self.father.printTree(prefix + "        ")
        if type(self.mother) == type("cat") :
            print(prefix + "mother: "+self.mother)
        else : 
            print(prefix + "mother: ")
            self.mother.printTree(prefix + "        ")
        
# create a class for Family trees which has two method functions
# init which takes 3 arguments, the root person's name, either a string or a FamilyTree for the father, and the same for the mother
# printTree which takes 1 argument, a prefix string for the string

class FamilyTree :
    def __init__(self,name,father,mother) :
    def printTree(self,prefix) :


>>> f = FamilyTree("Steve","Sam","Sarah")
>>> m = FamilyTree("Norma","Norman","Nancy")
>>> me = FamilyTree("Snoopy",f,m)
>>> me.printTree("")
Snoopy
father: 
        Steve
        father: Sam
        mother: Sarah
mother: 
        Norma
        father: Norman
        mother: Nancy
>>> me.printTree("tree | ")
tree | Snoopy
tree | father: 
tree |         Steve
tree |         father: Sam
tree |         mother: Sarah
tree | mother: 
tree |         Norma
tree |         father: Norman
tree |         mother: Nancy
>>> me = FamilyTree("Woodstock","unknown",m)
>>> me.printTree("lopsided | ")
lopsided | Woodstock
lopsided | father: unknown
lopsided | mother: 
lopsided |         Norma
lopsided |         father: Norman
lopsided |         mother: Nancy
>>>