Smart contract is a computer protocol designed to spread,verify or execute contracts in an information-based manner.

　　Smart contract is a set of commitments defined in digital form,which control digital assets and contain rights and obligations agreed by contract participants,and is automatically executed by computer system.

　　The smart contract program is not only a computer program that can be executed automatically,but also a system participant.It can respond to the received information,receive and store value,and send information and value to the outside

　　智能合約的全生命周期包括：合約生成、合約發(fā)布和合約執(zhí)行。

　　合約生成：其中合約規(guī)范和合約驗(yàn)證至關(guān)重要。

　　合約發(fā)布：需要多個(gè)節(jié)點(diǎn)進(jìn)行共識(shí)和驗(yàn)證。

　　合約執(zhí)行：基于“事件觸發(fā)”，智能合約會(huì)定期遍歷每個(gè)合約的狀態(tài)機(jī)和觸發(fā)條件，將滿足觸發(fā)條件的合約推送到驗(yàn)證隊(duì)列。

　　合約實(shí)現(xiàn)：通過(guò)賦予對(duì)象數(shù)字特性，將對(duì)象程序化并部署在區(qū)塊鏈上，同時(shí)改變數(shù)字對(duì)象的狀態(tài)（如分配轉(zhuǎn)移）和數(shù)值。

　　從部署的智能合約中讀取數(shù)據(jù)：

　　import json

　　from web3 importWeb3,HTTPProvider

　　from web3.contract importConciseContract

　　#compile your smart contract with truffle first

　　truffleFile=json.load(open('./build/contracts/greeter.json'))

　　abi=truffleFile['abi']源碼案例技術(shù)I35流程7O98詳細(xì)O7I8

　　bytecode=truffleFile['bytecode']

　　#web3.py instance

　　w3=Web3(HTTPProvider("https://ropsten.infura.io/<ApI Key here>"))

　　print(w3.isConnected())

　　contract_address=Web3.toChecksumAddress("<Deployed Contract Address here>")

　　#Instantiate and deploy contract

　　contract=w3.eth.contract(abi=abi,bytecode=bytecode)

　　#Contract instance 開(kāi)發(fā)功能：MrsFu123

　　contract_instance=w3.eth.contract(abi=abi,address=contract_address)

　　#Contract instance in concise mode

　　#contract_instance=w3.eth.contract(abi=abi,address=contract_address,ContractFactoryClass=ConciseContract)

　　#Getters+Setters for web3.eth.contract object ConciseContract

　　#print(format(contract_instance.getGreeting()))

　　print('Contract value:{}'.format(contract_instance.functions.getGreeting().call()))