智能合约：从 Python 调用智能合约
以太坊带来了智能合约的进步，其是可公开验证的代码。如果我们改变合约状态，我们将花费一些gas。现在，让我们创建一个Python程序，它可以在以太坊上调用智能合约。因为我们不想实验中支付费用，所以我们将运行Ganache，这是一个本地以太坊实例。
首先，我们去并添加我们的代码：
我们添加的代码中包括add()， sub()， mul()， sqr()和sqrt()函数：
pragma solidity ^0.8.0;contract mymath {function sqrt(uint x) public view returns (uint y) {uint z = (x + 1) / 2;y = x;while (z < y) {y = z;z = (x / z + z) / 2;}}function sqr(uint a) public view returns (uint) {uint c = a * a;return c;}function mul(uint a, uint b) public view returns (uint) {uint c = a * b;return c;}function sub(uint a, uint b) public view returns (uint) {return a - b;}function add(uint a, uint b) public view returns (uint) {uint c = a + b;return c;}}
现在编译我们的智能合约，并生成ABI(应用程序二进制接口)。通过ABI，我们可以创建智能合约中所有数据元素和函数。这通常用JSON格式定义。在我们的例子中，ABI是(可以从Remix中的ABI复制按钮中复制):
{"inputs": [{"internalType": "uint256","name": "a","type": "uint256"},{"internalType": "uint256","name": "b","type": "uint256"}],"name": "add","outputs": [{"internalType": "uint256","name": "","type": "uint256"}],"stateMutability": "view","type": "function"},{"inputs": [{"internalType": "uint256","name": "a","type": "uint256"},{"internalType": "uint256","name": "b","type": "uint256"}],"name": "mul","outputs": [{"internalType": "uint256","name": "","type": "uint256"}],"stateMutability": "view","type": "function"},{"inputs": [{"internalType": "uint256","name": "a","type": "uint256"}],"name": "sqr","outputs": [{"internalType": "uint256","name": "","type": "uint256"}],"stateMutability": "view","type": "function"},{"inputs": [{"internalType": "uint256","name": "x","type": "uint256"}],"name": "sqrt","outputs": [{"internalType": "uint256","name": "y","type": "uint256"}],"stateMutability": "view","type": "function"},{"inputs": [{"internalType": "uint256","name": "a","type": "uint256"},{"internalType": "uint256","name": "b","type": "uint256"}],"name": "sub","outputs": [{"internalType": "uint256","name": "","type": "uint256"}],"stateMutability": "view","type": "function"}
接下来，我们运行 Ganache：
然后可以选择Ganache作为我们的环境：
下一步部署智能合约：
现在可以看到合约已经部署到了Block 2。合约已部署到以下地址：
0x1aC3CD1b37898ed4D3005f3C12b4425A6eFFDc30
对于Ganache，我们在端口 8545运行它，并可以通过web.Web()连接到它。然后可以将ABI数据压缩为一个字符串。我们可以使用we3.eth.contract()调用该合约：
import web3w3 = web3.Web3(web3.HTTPProvider('http://127.0.0.1:8545'))abi="[{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"a\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"b\",\"type\":\"uint256\"}],\"name\":\"add\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"a\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"b\",\"type\":\"uint256\"}],\"name\":\"mul\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"a\",\"type\":\"uint256\"}],\"name\":\"sqr\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"x\",\"type\":\"uint256\"}],\"name\":\"sqrt\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"y\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"a\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"b\",\"type\":\"uint256\"}],\"name\":\"sub\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"}]"c = w3.eth.contract(address='0x1aC3CD1b37898ed4D3005f3C12b4425A6eFFDc30', abi=abi)a=5b=4rtn= c.caller().add(a,b)print(f"{a}+{b}={rtn}")rtn= c.caller().mul(a,b)print(f"{a}*{b}={rtn}")rtn= c.caller().sub(a,b)print(f"{a}-{b}={rtn}")rtn= c.caller().sqr(a)print(f"sqr({a})={rtn}")rtn= c.caller().sqrt(a)print(f"sqrt({a})={rtn}")
现在我们可以简单地调用智能合约中的函数，形式如下:
rtn= c.caller().add(a,b)print(f"{a}+{b}={rtn}")
下面的代码运行示例验证了对智能合约的调用：
% **python web.py**5+4=95*4=205-4=1sqr(5)=25sqrt(5)=2
我们需要做的就是编译智能合约并部署它，然后记录智能合约和ABI的地址，最后调用智能合约中的功能。
Source：/@billatnapier/calling-smart-contracts-from-python-977a8a9190e2
关于
ChinaDeFi- 是一个研究驱动的DeFi创新组织，同时我们也是区块链开发团队。每天从全球超过500个优质信息源的近900篇内容中，寻找思考更具深度、梳理更为系统的内容，以最快的速度同步到中国市场提供决策辅助材料。
Layer 2道友- 欢迎对Layer 2感兴趣的区块链技术爱好者、研究分析人与Gavin（微信: chinadefi）联系，共同探讨Layer 2带来的落地机遇。敬请关注我们的微信公众号“去中心化金融社区”。
