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トランザクションを発行するBot作成の道のり その②～スマートコントラクトの実行～
はじめに
前回からの続き。
前回はウォレット残高を確認するのみでしたが、今回は特定のスマートコントラクトを実行するまでやってみます。
イーサリアムとスマートコントラクトって？
スマートコントラクトが生成されるまでの流れは以下の通りで、コンパイルされたコードがブロックチェーンに登録されると実行可能となり、その際には「Contract」アカウントが発行されます。
https://book.ethereum-jp.net/first_use/contract
コンパイル済みのコードをトランザクションに付加してネットワークに送信する。
トランザクションがブロックチェーンに登録されることで「Contract」アカウントが生成されそのアドレスが発行される。
ユーザー「Contract」アカウントへトランザクションを発行することによりスマートコントラクトを実行する
そのため、トランザクションを送信する際には、「Contract」アカウントのアドレスが必要となります。
加えて、そのコントラクトがどのような仕様なのかをあらわすABI (Application Binary Interface)が必要となる。
ABIとはContractの取り扱い説明書のようなものです。例えば、このContractがどのような名前の関数が定義されているか、それぞれの関数にアクセスするために、どのような型のパラメータを渡す必要があるか、関数の実行結果はどのような型のデータが返るか、などの情報が含まれたものです。
この2つがあることで、どこにどのような形式でトランザクションを流ればいいかが明らかになる。
実装（コントラクト実行まで）
とある世界一有名と思われるNFTコレクションのコントラクトの実行までを行ってみます。
スマートコントラクトのアドレスやABIはetherscanなどで確認することができます。
https://etherscan.io/address/0xb47e3cd837ddf8e4c57f05d70ab865de6e193bbb#code
これらをweb3.pyで設定して実行することで、「Contract」アカウントへトランザクションを発行することができます。
from web3 import Web3
# 確認したい対象のウォレットアドレス
myWalletAddress = "0xxxxxxxxxxxx"
# RPCのURL
web3 = Web3(Web3.HTTPProvider("https://eth.llamarpc.com"))
isConnected = web3.isConnected()
# ABI
abi = '''
[{"constant":true,"inputs":[],"name":"name","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"punksOfferedForSale","outputs":[{"name":"isForSale","type":"bool"},{"name":"punkIndex","type":"uint256"},{"name":"seller","type":"address"},{"name":"minValue","type":"uint256"},{"name":"onlySellTo","type":"address"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"punkIndex","type":"uint256"}],"name":"enterBidForPunk","outputs":[],"payable":true,"type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"punkIndex","type":"uint256"},{"name":"minPrice","type":"uint256"}],"name":"acceptBidForPunk","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"name":"","type":"uint8"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"addresses","type":"address[]"},{"name":"indices","type":"uint256[]"}],"name":"setInitialOwners","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"withdraw","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"imageHash","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"nextPunkIndexToAssign","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"punkIndexToAddress","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"standard","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"punkBids","outputs":[{"name":"hasBid","type":"bool"},{"name":"punkIndex","type":"uint256"},{"name":"bidder","type":"address"},{"name":"value","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"balanceOf","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"allInitialOwnersAssigned","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"allPunksAssigned","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"punkIndex","type":"uint256"}],"name":"buyPunk","outputs":[],"payable":true,"type":"function"},{"constant":false,"inputs":[{"name":"to","type":"address"},{"name":"punkIndex","type":"uint256"}],"name":"transferPunk","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"punkIndex","type":"uint256"}],"name":"withdrawBidForPunk","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"to","type":"address"},{"name":"punkIndex","type":"uint256"}],"name":"setInitialOwner","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"punkIndex","type":"uint256"},{"name":"minSalePriceInWei","type":"uint256"},{"name":"toAddress","type":"address"}],"name":"offerPunkForSaleToAddress","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"punksRemainingToAssign","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"punkIndex","type":"uint256"},{"name":"minSalePriceInWei","type":"uint256"}],"name":"offerPunkForSale","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"punkIndex","type":"uint256"}],"name":"getPunk","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"pendingWithdrawals","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"punkIndex","type":"uint256"}],"name":"punkNoLongerForSale","outputs":[],"payable":false,"type":"function"},{"inputs":[],"payable":true,"type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"punkIndex","type":"uint256"}],"name":"Assign","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"from","type":"address"},{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Transfer","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"from","type":"address"},{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"punkIndex","type":"uint256"}],"name":"PunkTransfer","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"punkIndex","type":"uint256"},{"indexed":false,"name":"minValue","type":"uint256"},{"indexed":true,"name":"toAddress","type":"address"}],"name":"PunkOffered","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"punkIndex","type":"uint256"},{"indexed":false,"name":"value","type":"uint256"},{"indexed":true,"name":"fromAddress","type":"address"}],"name":"PunkBidEntered","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"punkIndex","type":"uint256"},{"indexed":false,"name":"value","type":"uint256"},{"indexed":true,"name":"fromAddress","type":"address"}],"name":"PunkBidWithdrawn","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"punkIndex","type":"uint256"},{"indexed":false,"name":"value","type":"uint256"},{"indexed":true,"name":"fromAddress","type":"address"},{"indexed":true,"name":"toAddress","type":"address"}],"name":"PunkBought","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"punkIndex","type":"uint256"}],"name":"PunkNoLongerForSale","type":"event"}]
'''
# コントラクトアドレス
contract = "0xb47e3cd837dDF8e4c57F05d70Ab865de6e193BBB"
if isConnected:
contract = web3.eth.contract(address=contract, abi=abi)
print(contract.functions.name().call())
print(contract.functions.symbol().call())
balance = contract.functions.balanceOf(myWalletAddress).call()
print(web3.fromWei(balance, 'ether'))contract = web3.eth.contract(address=contract, abi=abi)
の部分で、コントラクトのオブジェクトを生成し、contract.functions.name().call()のようにして実行しています。
nameはetherscanでいうと以下の部分。引数なしなのでそのまま実行できています。
balance = contract.functions.balanceOf(myWalletAddress).call()
の部分では引数に自分のウォレットアドレスを指定して実行しています。
etherscanでいうと以下の部分。引数が必要になっていますね。
web3.pyにて、コントラクトアカウントのアドレスとABIを指定することで簡単にトランザクションを実行することができました。
Read系のContractの場合はこんな感じでかなり簡単に実行することができました。
次回はWrite系にチャレンジしてみます。