I am trying to write a python code that is un-decryptable. Is this possible there are things like pyarmor and such that would enable a secure source code but I am looking for something that is not decryptable to maximize the security. The aim is to create a secure close-sourced program in python.
Python is an interpreted language, which means that the interpreter needs the source code at runtime in order to work. This means that even if you were able to encrypt the source code, the interpreter would still need to decrypt the source code to work at all so there is no 100% safe option. There are a few tactics you may want to look into though:

Obfuscation, which works by making the source code less readable
Compilation, which converts the source to machine code (Cython does this I think), which makes it harder to reverse-engineer

Could you make a decryption interpreter for Python? Probably. Would the performance be terrible? Also likely. Is it much easier to do one of the two above? Definitely. Or just switch to a different language which supports compilation and instruction-level obfuscation (like C/C++, Java, or C#).
Creating a close sourced Python program