33. Working with bytes and encoding

`bytes` are immutable sequences of integers 0-255, distinct from `str` (Unicode text). Converting between them requires an explicit encoding, usually UTF-8.

python
b = b"\x01\x02\xff"
b.hex()                     # "0102ff"
bytes.fromhex("0102ff")     # b'\x01\x02\xff'

s = "gm"
s.encode("utf-8")           # b'gm'
b"gm".decode("utf-8")       # "gm"

import base64
base64.b64encode(b"gm")     # b'Z20='

Blockchain data (addresses, hashes, signatures) is often shown as `0x`-prefixed hex text but stored/transmitted as raw bytes; strip the prefix before `bytes.fromhex`.

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