markov first order text processing in python

Question

I wrote codes for text generating from a given text file. I use markov first order model. First create dictionary from text file. In case of punctuation ('.','?','!') it key is '$'. After creating dictionary I generate text randomly from the created dictionary. When it detect '$' it start new sentence. My code is given below:

import random

def createDictionary(fileName):

    '''Creates dictionary with following words for a word using a text input'''

    file = open(fileName, "r")
    text = file.read()
    file.close()
    LoW = text.split()
    LoW = ["$"] + LoW
    wd = {}
    index = 0
    while index < len(LoW):    ##Make dictionary entries
        word = LoW[index]
        if word not in wd:
            if word[-1] == "?" or word[-1] =="." or word[-1] =="!":
                word = "$"
            wd[word] = []
        index += 1

    index = 0

    while index < (len(LoW) - 1):   #Make list for each of those entries
        word = LoW[index]
        if word[-1] == "?" or word[-1] =="." or word[-1] =="!":
            word = "$"
        nextWord = LoW[index + 1]
        wd[word] += [nextWord]
        index += 1
    return wd

def generateText(d,n):

 """                                                                                                
    Return a genWord no more than the specified length using a first_order Markov model                         
    """

    current_word = random.choice(d['$'])
    genWord = current_word
    for i in range(n-1):
        if current_word not in d:
           break
        next_word = random.choice(d[current_word])

        current_word = next_word
        genWord = genWord + " " + next_word
    return genWord 

My text file('a.txt') is:

I am doing markov first order text processing in python. Will it work in my code? Nor I seek help from someone. I believe I made a naive mistake! but I could not fix it.

Input: d = createDictionary( 'a.txt' )

print generateText(d,50)

Output: 1 line out of 4 randomly.

Could anyone suggest me how could I fix this code so that it correctly generate inputted text?