How to generate a Bitcoin public key on a "calculator"?

Question

Python

Greetings. Can you please tell me how to manually calculate the Bitcoin public key for Legacy addresses? I know how to get uncompressed and compressed private key from HEX number. I know how to get an uncompressed and compressed address from an uncompressed and compressed public key. But I do not understand how and from what the public keys themselves are considered. Googled ECDSA and Secp256k1. Read articles about it on the Bitcoin Wiki. For several days I tried to understand, but could not. Tried to unpick the bit library for Python, but the concept didn't happen. Help understand. And, if it's not difficult, write the code in Python.

Answer 1

So damn it, which is easier, the source codes of bitcoin are open, I took and read the documentation. https://github.com/bitcoin/bitcoin