cryptos
Pure Python from-scratch zero-dependency implementation of Bitcoin
...It can parse and inspect legacy and SegWit transaction structures, although its transaction validation is intentionally incomplete compared with a full Bitcoin node. Block utilities cover headers, proof-of-work validation, and difficulty calculations. A lightweight network client can connect to Bitcoin peers, perform the protocol handshake, and request block headers. The implementation is intentionally slow and should be treated as learning code rather than production cryptocurrency software.