Answer to biostar https://www.biostars.org/p/138848/ Question: How to replace a set of sequence ID's with another set of sequence ID's ??

My answer to https://www.biostars.org/p/138848/ Question: How to replace a set of sequence ID's with another set of sequence ID's ??

Let us consider I have a file (Notepad or MS-doc) having 10 sequences with ID's A, B, C, D, E, F, G, H, I, J. I want to replace the ID's with K, L, M, N, O ,P, Q, R, S, T i.e., A to re replaced with K, B to be replaced with M and so on. How can I do this? I am a Biologist who have newly started analyzing Large data's and having this problem.  Any form of advice/help will be highly appreciated.