use the text and code :    cipher.txt xun gmr jznqymxu qzhhxzupmur ytmq dnvhq vavpncd vlvhpq mq txl xh mb ytn anhncxud lmii vpphnqq cnyxx nqenamviid vbynh ytn rxipnu rixgnq ltmat gnavcn v ozgmivuy axcmurxzy evhyd bxh ymcnq ze ytn cxfncnuy qenvhtnvpnp gd  exlnhbzi txiidlxxp lxcnu ltx tnienp hvmqn cmiimxuq xb pxiivhq yx bmrty qnkzvi tvhvqqcnuy vhxzup ytn axzuyhd     python code : #!/usr/bin/env python3 from collections import Counter import re TOP_K  = 20 N_GRAM = 3 # Generate all the n-grams for value n def ngrams(n, text):     for i in range(len(text) -n + 1):         # Ignore n-grams containing white space         if not re.search(r'\s', text[i:i+n]):            yield text[i:i+n] # Read the data from the ciphertext with open('ciphertext.txt') as f:     text = f.read() # Count, sort, and print out the n-grams for N in range(N_GRAM):    print("-------------------------------------")    print("{}-gram (top {}):".format(N+1, TOP_K))    counts = Counter(ngrams(N+1, text))        # Count    sorted_counts = counts.most_common(TOP_K)  # Sort     for ngram, count in sorted_counts:                          print("{}: {}".format(ngram, count))   # Print

use the text and code : 

cipher.txt

xun gmr jznqymxu qzhhxzupmur ytmq dnvhq vavpncd vlvhpq mq txl xh mb ytn

anhncxud lmii vpphnqq cnyxx nqenamviid vbynh ytn rxipnu rixgnq ltmat gnavcn

v ozgmivuy axcmurxzy evhyd bxh ymcnq ze ytn cxfncnuy qenvhtnvpnp gd 

exlnhbzi txiidlxxp lxcnu ltx tnienp hvmqn cmiimxuq xb pxiivhq yx bmrty qnkzvi

tvhvqqcnuy vhxzup ytn axzuyhd

python code :

#!/usr/bin/env python3

from collections import Counter

import re

TOP_K  = 20

N_GRAM = 3

# Generate all the n-grams for value n

def ngrams(n, text):

    for i in range(len(text) -n + 1):

        # Ignore n-grams containing white space

        if not re.search(r'\s', text[i:i+n]):

           yield text[i:i+n]

# Read the data from the ciphertext

with open('ciphertext.txt') as f:

    text = f.read()

# Count, sort, and print out the n-grams

for N in range(N_GRAM):

   print("-------------------------------------")

   print("{}-gram (top {}):".format(N+1, TOP_K))

   counts = Counter(ngrams(N+1, text))        # Count

   sorted_counts = counts.most_common(TOP_K)  # Sort 

   for ngram, count in sorted_counts:                  

       print("{}: {}".format(ngram, count))   # Print