def add_block(self, transactions):
    """
    add a block to block_chain
    """
    last_block = self.get_last_block()
    prev_hash = last_block.get_header_hash()
    height = last_block.block_header.height + 1
    block_header = BlockHeader('', height, prev_hash)
    # reward to wallets[0]
    wallets = Wallets()
    keys = list(wallets.wallets.keys())
    w = wallets[keys[0]]
    coin_base_tx = self.coin_base_tx(w.address)
    transactions.insert(0, coin_base_tx)
    block = Block(block_header, transactions)
    block.mine(self)
    block.set_header_hash()
    self.db.create(block.block_header.hash, block.serialize())
    last_hash = block.block_header.hash
    self.set_last_hash(last_hash)
    utxo = UTXOSet()
    utxo.update(block)

def _find_unspent_transactions(self, address):
    """
    Find all unspent transactions
    """
    spent_txos = {}
    unspent_txs = {}
    last_block = self.get_last_block()
    last_height = last_block.block_header.height
    # Reverse
    for height in range(last_height, -1, -1):
        block = self.get_block_by_height(height)
        for tx in block.transactions:
            txid = tx.txid
            # all outputs
            for vout_index, vout in enumerate(tx.vouts):
                txos = spent_txos.get(txid, [])
                # vout_index is spent
                if vout_index in txos:
                    continue
                if vout.can_unlock_output_with(address):
                    old_vouts = unspent_txs.get(tx, [])
                    old_vouts.append(vout)
                    unspent_txs[tx] = old_vouts
            if not tx.is_coinbase():
                for vin in tx.vins:
                    if vin.can_be_unlocked_with(address):
                        txid_vouts = spent_txos.get(txid, [])
                        txid_vouts.append(vin.vout)
                        spent_txos[vin.txid] = txid_vouts
    return unspent_txs

class UTXOSet(Singleton):
    FLAG = 'UTXO'
    def __init__(self, db_url='http://127.0.0.1:5984'):
        self.db = DB(db_url)

def reindex(self, bc):
    key = self.FLAG + "l"
    last_block = bc.get_last_block()
    if key not in self.db:
        utxos = bc.find_UTXO()
        for txid, index_vouts in utxos.items():
            key = self.FLAG + txid
            # outs = []
            for index_vout in index_vouts:
                vout = index_vout[1]
                index = index_vout[0]
                vout_dict = vout.serialize()
                vout_dict.update({"index": index})
                tmp_key = key + "-"+str(index)
                try:
                    self.db.create(tmp_key, vout_dict)
                except ResourceConflict as e:
                    print(e)
        if not last_block:
            return
        self.set_last_height(last_block.block_header.height)
    else:
        utxo_last_height = self.get_last_height()
        last_block_height = last_block.block_header.height
        for i in range(utxo_last_height, last_block_height):
            block = bc.get_block_by_height(i)
            self.update(block)

def find_spendable_outputs(self, address, amount):
    utxos = self.find_utxo(address)
    accumulated = 0
    spendable_utxos = []
    for ftxo in utxos:
        output = ftxo.txoutput
        accumulated += output.value
        spendable_utxos.append(ftxo)
        if accumulated >= amount:
            break
    return accumulated, spendable_utxos

def find_utxo(self, address):
    query = {
        "selector": {
            "_id": {
                "$regex": "^UTXO"
            },
            "pub_key_hash": address
        }
    }
    docs = self.db.find(query)
    utxos = []
    for doc in docs:
        index = doc.get("index", None)
        if index is None:
            continue
        doc_id = doc.id
        txid_index_str = doc_id.replace(self.FLAG, "")
        _flag_index = txid_index_str.find("-")
        txid = txid_index_str[:_flag_index]
        ftxo = FullTXOutput(txid, TXOutput.deserialize(doc), index)
        utxos.append(ftxo)
    return utxos

def update(self, block):
    for tx in block.transactions:
        txid = tx.txid
        key = self.FLAG + txid
        # add uxto
        for vout_index, vout in enumerate(tx.vouts):
            vout_dict = vout.serialize()
            vout_dict.update({"index": vout_index})
            tmp_key = key + "-" +str(vout_index)
            try:
                self.db.create(tmp_key, vout_dict)
            except ResourceConflict as e:
                print(e)
        # vins delete used utxo
        for vin in tx.vins:
            vin_txid = vin.txid
            key = self.FLAG + vin_txid + "-" +str(vin.vout)
            doc = self.db.get(key)
            if not doc:
                continue
            try:
                self.db.delete(doc)
            except ResourceNotFound as e:
                print(e)
    self.set_last_height(block.block_header.height)

# 創(chuàng)建創(chuàng)世塊
$python3 main.py
<wallet.Wallet object at 0x0000010AED8276A0> <wallet.Wallet object at 0x0000010AED827940>
19RUj6zvbrAXNnEtkuric5pYQJTkZy57nc 17AEyyKbeoEbfMa3jS8Uji6tVG37DrTJN9
Mining a new block
Found nonce == 53ash_hex == 0adfd71d90955ad9219871d8abe03ae83ef9f1f13f9a141ef6ca0ce2d16c93af
('conflict', 'Document update conflict.')
Block(_block_header=BlockHeader(timestamp='1551246051.6814992', hash_merkle_root='1f6cf2e68e8ab0dda1cc1550f85b4df85b83db3cc3af262b26a5a306121725be', prev_block_hash='', hash='ef20a87f2edc8589e813be60d534e736f51c45a3ec94e1918c18bce057afc89d', nonce=None, height=0))
Block(_block_header=BlockHeader(timestamp='1551246052.0582814', hash_merkle_root='3cf2c8514fdaac0cb2b6502f72cf267bcf9966042be28ee48eff61e4695a90f2', prev_block_hash='ef20a87f2edc8589e813be60d534e736f51c45a3ec94e1918c18bce057afc89d', hash='b0bdedf26575722a7efdf94db7dfa60c1c4dfe1483529ff04dd553d6828de718', nonce=53, height=1))
# 轉賬
$python3 cli.py send --from 19RUj6zvbrAXNnEtkuric5pYQJTkZy57nc --to 17AEyyKbeoEbfMa3jS8Uji6tVG37DrTJN9 --amount 10
Mining a new block
Found nonce == 20ash_hex == 07e91245d4e66b66279224980b0325c37d2f2e54a75402bdcd8fe55346cb3dcb
send 10 from 19RUj6zvbrAXNnEtkuric5pYQJTkZy57nc to 17AEyyKbeoEbfMa3jS8Uji6tVG37DrTJN9
# 查詢余額
$python3 cli.py balance 19RUj6zvbrAXNnEtkuric5pYQJTkZy57nc
19RUj6zvbrAXNnEtkuric5pYQJTkZy57nc balance is 1980

class MerkleNode(object):
    def __init__(self, left_node, right_node, data):
        self.left = left_node
        self.right = right_node
        if not self.left and not self.right:
            self.data = sum256_hex(data)
        else:
            data = self.left.data + self.right.data
            self.data = sum256_hex(data)
class MerkleTree(object):
    def __init__(self, datas):
        nodes = []
        for data_item in datas:
            node = MerkleNode(None, None, data_item)
            nodes.append(node)
        for _ in range(len(datas)//2):
            new_level = []
            for j in range(0, len(nodes), 2):
                if j + 1 >= len(nodes):
                    node = MerkleNode(nodes[j], "", None)
                else:
                    node = MerkleNode(nodes[j], nodes[j+1], None)
                new_level.append(node)
            nodes = new_level
        self.root_node = nodes[0]
    @property
    def root_hash(self):
        return self.root_node.data

if j + 1 >= len(nodes):
    node = MerkleNode(nodes[j], "", None)

@property
def root_hash(self):
    return self.root_node.data

5 2 OP_ADD 7 OP_EQUAL

<signature> <pubKey> OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG