I am trying to use Python to parse Uniswap swap event data from Etherscan. Here is the code for obtaining the swap event log:

import requests

etherscan_api = 'https://api.etherscan.io/api'
etherscan_api_key = 'ETHERSCAN_API_KEY'
pool_address = '0x5777d92f208679DB4b9778590Fa3CAB3aC9e2168' #DAU/USDC pool

swap_topic = '0xc42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67'

params = {
    'module': 'logs',
    'action': 'getLogs',
    'address': pool_address,
    'fromBlock': 15591456,
    'toBlock': 15591456,
    'topic0': swap_topic,
    'page': 1,
    'offset': 1000,
    'apikey': etherscan_api_key

resp = requests.get(url=etherscan_api, params=params)

which returns

[{'address': '0x5777d92f208679db4b9778590fa3cab3ac9e2168',
  'topics': ['0xc42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67',
  'data': '0xfffffffffffffffffffffffffffffffffffffffffffffff7cf3dd2f5c2526afa000000000000000000000000000000000000000000000000000000000901ae820000000000000000000000000000000000000000000010c70158041addb5d04a00000000000000000000000000000000000000000003717214bf888b6de019b6fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffbc89c',
  'blockNumber': '0xede820',
  'blockHash': '0x173abb50387b29add553b4e1fc3154d02f0fc55c277738bd8d16d3d8022ae76d',
  'timeStamp': '0x632cce2b',
  'gasPrice': '0x2ba5552a7',
  'gasUsed': '0x20d7a',
  'logIndex': '0xb6',
  'transactionHash': '0x63e6d27fdbea0968fb10130e59dfa1b79d18074a971ed5cbd7c25cfe32c1f1e3',
  'transactionIndex': '0x34'}]

I expect that the data field contains the swap information (sender, receiver, amounts, etc.) How do I actually parse it?

1 Answer 1


You can decode it this way:

const Web3 = require("web3");

const web3 = new Web3("");

const data =

// Swap(address,address,int256,int256,uint160,uint128,int24) // keccak256 hash of this signature is:
// c42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67 // the topic

// Swap(
//     address indexed sender,
//     address indexed recipient,
//     int256 amount0,
//     int256 amount1,
//     uint160 sqrtPriceX96,
//     uint128 liquidity,
//     int24 tick
// )

const decoded = web3.eth.abi.decodeParameters(
  // Decoding event data. Exclude the `indexed` parameters.
  ["int256", "int256", "uint160", "uint128", "uint24"],

console.log("decoded: ", decoded);

In the data field, we have the values of the non-indexed event params. The indexed param data are topics themselves and are not included in the data. Thus, when decoding the data, we need to indicate the non-indexed params.

I calculated the keccak256 hash of the Swap(address,address,int256,int256,uint160,uint128,int24) event signature to make sure it is the same topic as the one you have, and it is. Check yourself here: https://emn178.github.io/online-tools/keccak_256.html

So, just use web3.eth.abi.decodeParameters(arrayOfNonIndexedTypes,data) to decode your data.

In this case, the result is:

decoded:  Result {
  '0': '-151087372770986530054',
  '1': '151105154',
  '2': '79228862628487947997258',
  '3': '4162509295296294057679286',
  '4': '16500892',
  __length__: 5

I'm not sure if that data makes sense to you.

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