bitcoin block hash (python)

block_hash.py

import requests
import hashlib
import struct


def load_block_data(block_hash):
    r = requests.get('https://blockchain.info/ko/rawblock/' + block_hash)
    return r.json()


def block_hash(version: int,
               prevblock,
               merkle_root,
               time: int,
               bits: int,
               nonce: int):
    
    prevblock_little = bytearray.fromhex(prevblock)[::-1]
    merkle_root_little = bytearray.fromhex(merkle_root)[::-1]

    # pack binary little endian
    header_bin = struct.pack(
        # < : little endian
        # i : signed int (32 bit) - +
        # I : unsigned int (32 bit) +
        # 32s : 32 byte (char)

        # <i32s32sIII = little endian | int | byte[32] | byte[32] | unsigned int | unsigned int | unsigned int
        '<i32s32sIII',
        version,
        prevblock_little,  # little -> big
        merkle_root_little,  # little -> big
        time,
        bits,
        nonce,
    )
    # double hash
    h = hashlib.sha256(
        hashlib.sha256(header_bin).digest()
    ).digest()

    return h


# load block data from blockchain info
block = load_block_data("000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f")

# calculate block hash
hashed_block_header = block_hash(
    version=block['ver'],
    prevblock=block['prev_block'],
    merkle_root=block['mrkl_root'],
    time=block['time'],
    bits=block['bits'],
    nonce=block['nonce'],
)

# block hash to hex string
hex = hashed_block_header[::-1].hex()

print(hex)