Markov chains Implementation in python. I am implementing markov chains to find and replace the corrupted character in a string with the most...

Markov chains Implementation in python. I am implementing markov chains to find and replace the corrupted character in a string with the most probable character from the markov model of order k. I have successfully done 90% of the assignment but I am stuck at a small thing. Let me explain : 

Original : it was the best of times, it was the worst of times. 

Noisy : it w~s th~ bes~ of tim~s, i~ was ~he wo~st of~times.

I am able to replace 90% of the '~' from the string but only one or two values are wrong. I can share my code if anyone is willing to help.