用Web3.py、Infura和Graph查詢以太坊數(shù)據(jù)
本文我們將使用Web3.py這個(gè)Python庫(kù)直接查詢以太坊數(shù)據(jù)。Web3.py是一個(gè)為與Ethereum區(qū)塊鏈交互而建立的Python庫(kù)。有了它，我們可以為去中心化的應(yīng)用程序建立各種核心功能。我們可以直接與智能合約互動(dòng)，收集區(qū)塊鏈數(shù)據(jù)，并發(fā)送交易。讓我們開(kāi)始安裝Web3.py。
pip install web3
from web3 importWeb3
w3 = Web3(Web3.HTTPProvider('https://mainnet.infura.io/v3/YOUR_PROJECT_ID'))
# Get information about the latest block
w3.eth.getBlock('latest')
# Get the ETH balance of an address
w3.eth.getBalance('YOUR_ADDRESS_HERE')
https://zapper.fi/dashboard）這樣的產(chǎn)品功能，跟蹤我們代幣的美元價(jià)值如何？首先，需要掃描我們的地址，看看持有哪些代幣。為了做到這一點(diǎn)，我們將與各個(gè)代幣的智能合約進(jìn)行交互。這些合約的地址看起來(lái)像我們的錢(qián)包地址，只不過(guò)這些是合約地址。在這個(gè)地址上有智能合約代碼。代幣將遵守ERC-20標(biāo)準(zhǔn)，使我們更容易與這些合約進(jìn)行交互。一個(gè)ERC-20合約默認(rèn)具有以下功能：
function name() public view returns (string)
function symbol() public view returns (string)
function decimals() public view returns (uint8)
function totalSupply() public view returns (uint256)
function balanceOf(address _owner) public view returns (uint256 balance)
function transfer(address _to, uint256 _value) public returns (bool success)
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success)
function approve(address _spender, uint256 _value) public returns (bool success)
function allowance(address _owner, address _spender) public view returns (uint256 remaining)
balanceOf是讓我們看到我們查詢的錢(qián)包地址持有多少代幣的函數(shù)。
import json
ABI = json.loads('[{"constant":true,"inputs":[{"name":"_owner","type":"address"}],"name":"balanceOf",
"outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}]')
wallet_address = 'YOUR_ADDRESS_HERE'
wallet_address = Web3.toChecksumAddress(wallet_address)
token_contract_address = '0xc011a73ee8576fb46f5e1c5751ca3b9fe0af2a6f'
token_contract_address = Web3.toChecksumAddress(token_contract_address)
# define contract
contract = w3.eth.contract(token_contract_address, abi=ABI)
# call contract and get data from balanceOf for argument wallet_address
raw_balance = contract.functions.balanceOf(wallet_address).call()
# convert the value from Wei to Ether
synthetix_value = Web3.fromWei(raw_balance, 'ether')
toChecksumAddress()來(lái)確保我們的地址是校驗(yàn)格式的。我們使用 fromWei()將我們的Wei價(jià)格轉(zhuǎn)換為 ether。1ETH是1E18 Wei。
from gql import gql, Client
from gql.transport.requests importRequestsHTTPTransport
sample_transport=RequestsHTTPTransport(
url='https://api.thegraph.com/subgraphs/name/uniswap/uniswap-v2',
verify=True,
retries=5,
)
client = Client(
transport=sample_transport
)
# Get the value of SNX/ETH
query = gql('''
query {
pair(id: "0x43ae24960e5534731fc831386c07755a2dc33d47"){
reserve0
reserve1
}
}
''')
response = client.execute(query)
snx_eth_pair = response['pair']
eth_value = float(snx_eth_pair['reserve1']) / float(snx_eth_pair['reserve0'])
# Get the value of ETH/DAI
query = gql('''
query {
pair(id: "0xa478c2975ab1ea89e8196811f51a7b7ade33eb11"){
reserve0
reserve1
}
}
''')
response = client.execute(query)
eth_dai_pair = response['pair']
dai_value = float(eth_dai_pair['reserve0']) / float(eth_dai_pair['reserve1'])
snx_dai_value = eth_value * dai_value
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