Cassacius mini private key to WIF in pure Python 3.6

minikey-to-wif.py

import hashlib

MINIKEY = "S6c56bnXQiBjk9mqSYE7ykVQ7NzrRy"

ALPHABET = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'

def sha256(x):
    return hashlib.sha256(x).digest()


def base58check_encode(x):
    checksum = sha256(sha256(x))[:4]
    data = x + checksum

    num = int.from_bytes(data, "big")
    encode = []
    while (num > 0):
        num, res = divmod(num, len(ALPHABET))
        encode.append(ALPHABET[res])
    return "".join(reversed(encode))


def minikey_to_privkey(mk):
    assert mk[0] == "S", "not a mini key (invalid start character)"
    assert len(mk) == 30, "not a mini key (invalid length)"
    digest = sha256(mk.encode() + b"?")
    assert digest[0] == 0, f"not a mini key (invalid hash: {digest.hex()})"
    return sha256(mk.encode())


def privkey_to_wif(pk):
    return base58check_encode(b"\x80" + pk)


privkey = minikey_to_privkey(MINIKEY)
print("private key hex:", privkey.hex())
wif = privkey_to_wif(privkey)
print("wif format:", wif)