gistfile1.txt

My last version what I got was

filename = 'abc.txt'
new_dict ={}
total_count = 0

# opening the filename in read mode
with open(filename, "r") as fp:
# iterating through each line in file    
    for line in fp:
# splitting the words in each line        
        words = line.split()

# Iterating through each word to store in dictionary
        for word in words:         
            word = word.lower()
# if we are seeing a word first time assign the value 1            
        if not word in new_dict:
             new_dict[word] = 1
# if the word already exists in dictionary increment the frequency of word
        else:
            new_dict[word] +=1
            total_count +=1
for word in new_dict:            
 probab = new_dict[word]/ total_count
 print('probability of word '+ word +': ' + str(probab))

output_file = 'x.txt'
with open(output_file, "w") as fs:
    for word in new_dict:
           fs.write('probability for word '+ word +'is: ' + str(probab) + '\n')