I got sick of using remix and copying-pasting my web3 deploy text so I'm trying to write a python script that will generate this deploy test for me. However, one of the fields in the instantiation code is data, and it holds a bytecode representation of the contract. How can I generate this bytecode as well? I'm unable to use py-solc for some reason (when I type from solc import * I get a ModuleNotFound error) so if I could recreate this bytecode manually that'd be awesome.

Here's an example of what I'm trying to do:

for smart contract "Storage.sol" below:

pragma solidity ^0.4.0;

contract Storage {
    uint storedData;
    address lastSetter;
    function set(uint x) public {
        storedData = x;
        lastSetter = msg.sender;

    function get() public constant returns (uint) {
        return storedData;

    function getLastSetter() public constant returns (address) {
      return lastSetter;

Remix generates this web3 deploy:

var storageContract = web3.eth.contract([{"constant":true,"inputs":[],"name":"getLastSetter","outputs":[{"name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"x","type":"uint256"}],"name":"set","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"get","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}]);
var storage = storageContract.new(
     from: web3.eth.accounts[0], 
     data: * long hex number *, 
     gas: '4700000'
   }, function (e, contract){
    console.log(e, contract);
    if (typeof contract.address !== 'undefined') {
         console.log('Contract mined! address: ' + contract.address + ' transactionHash: ' + contract.transactionHash);

My script can make this:

var storageContract = web3.eth.contract([{"constant":false,"inputs":[{"name":"x","type":"uint256"}],"name":"set","outputs":[],"payable":false,"stateMutability":"type":"function"},{"constant":true,"inputs":[],"name":"get","outputs":[],"payable":false,"stateMutability":"type":"function"},{"constant":true,"inputs":[],"name":"getLastSetter","outputs":[],"payable":false,"stateMutability":"type":"function"},])
var storage = storageContract.new(
        from: web3.eth.accounts[0],
        data: '',
        gas: '470000'
    }, function(e, contract){
        console.log(e, contract);
        if (typeof contract.address != 'undefined') {
          console.log('Contract successfully mined. address: ' + contract.address + ' transactionHash: ' + contract.transactionHash);

(still figuring out the statemutability (what even is that?) and output parsing as well, but thats a question for another day)

To sum up, I am trying to write a Python script that goes from solidity to the 'web3 deploy' text remix generates. How can I generate the required bytecode field?

Edit: I bit the bullet and tackled my installation of py-solc again. Got it right this time; I was accidentally installing using pip2.x rather than pip3.x. I'd still like to know how py-solc generates the bytecode, but the project works know. Thanks all for your help

  • You should use a framework like populus or truffle to automate deployment.
    – Ismael
    Commented Jan 2, 2018 at 1:56
  • @Ismael I could do that, but how could I make this tool work? I was using truffle but found the testing and deployment process cumbersome and slow whereas being able to whip up a deployable web3 text and throw it into geth would make things quicker to me
    – steve
    Commented Jan 2, 2018 at 2:25

1 Answer 1


You need to use the Solidity compiler (solc) to compile your Solidity code into bytecode. If you can't use Remix or py-solc, you could try just installing solc directly and shelling out to it. But I would recommend figuring out what went wrong in your py-solc installation. I use py-solc and find it quite easy to use.


The ABI (the part that includes "stateMutability") will also be emitted by the Solidity compiler.

  • Thanks! I will look into what happened. I got a ModuleNotFound error so I probably didn't install it in the right place
    – steve
    Commented Jan 2, 2018 at 12:23

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