The Mining Process � Step by Step

import hashlib, time, struct

def double_sha256(data: bytes) -> bytes:
    return hashlib.sha256(hashlib.sha256(data).digest()).digest()

def compact_to_target(bits: int) -> int:
    """Convert compact 'bits' field to 256-bit target integer"""
    exponent = bits >> 24
    mantissa = bits & 0x7FFFFF
    return mantissa * (256 ** (exponent - 3))

def mine_block(prev_hash: str, merkle_root: str, bits: int,
               version: int = 0x20000000) -> dict:
    """Full mining loop � returns first valid block found"""
    target = compact_to_target(bits)
    timestamp = int(time.time())
    nonce = 0
    attempts = 0
    start = time.time()

    # Pack header (80 bytes): version(4) + prev(32) + merkle(32) + time(4) + bits(4) + nonce(4)
    prev_bytes = bytes.fromhex(prev_hash.zfill(64))
    merkle_bytes = bytes.fromhex(merkle_root.zfill(64))

    while True:
        header = struct.pack("<I", version) + prev_bytes + merkle_bytes +                  struct.pack("<III", timestamp, bits, nonce)
        block_hash = double_sha256(header)
        hash_int = int.from_bytes(block_hash, "big")
        attempts += 1

        if hash_int < target:
            elapsed = time.time() - start
            return {
                "nonce": nonce,
                "hash": block_hash[::-1].hex(),  # Reverse for display (Bitcoin convention)
                "hash_int": hash_int,
                "target": target,
                "attempts": attempts,
                "time_s": round(elapsed, 4),
                "hash_rate": round(attempts / max(elapsed, 0.001)),
            }

        nonce = (nonce + 1) & 0xFFFFFFFF  # Wrap at 4 bytes
        if nonce == 0:
            # Nonce exhausted � change timestamp to reset search space
            timestamp += 1

# Mine with very easy difficulty (for demonstration speed)
easy_bits = 0x207fffff  # Easiest Bitcoin target
result = mine_block(
    prev_hash="0" * 64,
    merkle_root="a1b2c3d4e5f6" + "0" * 52,
    bits=easy_bits,
)
print(f"Block mined!")
print(f"  Nonce    : {result['nonce']:,}")
print(f"  Attempts : {result['attempts']:,}")
print(f"  Time     : {result['time_s']}s")
print(f"  Hash rate: {result['hash_rate']:,} H/s")
print(f"  Hash     : {result['hash'][:20]}...")