Failed token purchase transactions on uniswap with web3.py

Question

I'm getting failed transactions(reverted) when I try to buy tokens from uniswap v2 using the swapExactEthForToken method in my build transaction with web3.py. I have added my code below. I have tried this on ropsten, rinkeby and even mainnet. I have test ETH on both test networks also.

Any help will be greatly appreciated.

from web3 import Web3
import json
import config
import time
import pprint


infura_url = config.INFURA_URL_TESTNET
web3 = Web3(Web3.HTTPProvider(infura_url))

print(web3.isConnected())

# uniswap address and abi
uniswap_router = '0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D'
uniswap_factory = web3.toChecksumAddress('0x5c69bee701ef814a2b6a3edd4b1652cb9cc5aa6f')
uniswapABI = 'I pasted the uniswap v2 abi here'
uniswap_factory_abi = json.loads(uniswapABI)



sender_address = "0x39DC57cf562736D62bE25EFC1B37ce43dEaf51Bc"

balance = web3.eth.get_balance(sender_address)
eth_bal = web3.fromWei(balance, 'ether')
print('My Test Eth Balance is: ', eth_bal)

tokenToBuy = web3.toChecksumAddress("0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984")
spend = web3.toChecksumAddress("0xc778417E063141139Fce010982780140Aa0cD5Ab")  # wbnb contract


# Setup the Uniswap contract
contract = web3.eth.contract(address=uniswap_factory, abi=uniswap_factory_abi)

nonce = web3.eth.get_transaction_count(sender_address)


start = time.time()


uniswapv2_txn = contract.functions.swapExactETHForTokens(
    10000000000,  # set to 0, or specify minimum amount of tokeny you want to receive - consider decimals!!!
    [spend, tokenToBuy],
    sender_address,
    (int(time.time()) + 100000)
).buildTransaction({
    'from': sender_address,
    'value': web3.toWei(0.01, 'ether'),  
    'gas': 2000000,
    'nonce': nonce,
})

signed_txn = web3.eth.account.sign_transaction(uniswapv2_txn, private_key=config.private)
tx_token = web3.eth.send_raw_transaction(signed_txn.rawTransaction)
print(web3.toHex(tx_token))

Answer 1

I think you need to specify the router address and not the factory address to execute a trade....

Answer 2

Try this code :

Contract_Address = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D

from web3 import Web3
import json
from dotenv import load_dotenv
import time
import os
from web3.middleware import geth_poa_middleware


load_dotenv()

infura_url = os.getenv("INFURA_URL")
web3 = Web3(Web3.HTTPProvider(infura_url))
web3.middleware_onion.inject(geth_poa_middleware, layer=0)

print(web3.isConnected())

# uniswap address and abi
abi = json.load(open('abi.json'))
address = '0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D'
contract = web3.eth.contract(address=address, abi=abi)

sender_address = "0x5A9cBc9821cF17eC0823593b6a2daD9e72a053BC"

balance = web3.eth.get_balance(sender_address)
eth_bal = web3.fromWei(balance, 'ether')
print('My Test Eth Balance is: ', eth_bal)

tokenToBuy = web3.toChecksumAddress("0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984")   #Uni Token Address
spend = web3.toChecksumAddress("0xc778417E063141139Fce010982780140Aa0cD5Ab")  # wbnb contract # weth Token address

nonce = web3.eth.get_transaction_count(sender_address)

uniswapv2_txn = contract.functions.swapExactETHForTokens(
    10000000000,  # set to 0, or specify minimum amount of tokeny you want to receive - consider decimals!!!
    [spend, tokenToBuy],
    sender_address,
    (int(time.time()) + 100000)
).buildTransaction({
    'from': sender_address,
    'value': web3.toWei(0.1, 'ether'),  
    'gas': 2000000,
    'nonce': nonce,
})

signed_txn = web3.eth.account.sign_transaction(uniswapv2_txn, private_key=os.getenv("PRIVATE_KEY"))
tx_token = web3.eth.send_raw_transaction(signed_txn.rawTransaction)
print(web3.toHex(tx_token))

Answer 3

I think the problem is that you are using the factory contract instead of the router. Take a look at this code, with comments!

Note that I did not specify the token to buy, and this is based on mainnet ETH.

Keep in mind that these contracts on testnets often have issues, especially thinking that Ropsten and Rinkeby are considered deprecated. Also, you could use an environment variable for the private key to be safer.

from web3 import Web3
import json
import time

# Define the node URL and connection
node_url = "YOUR_NODE_URL"

web3 = Web3(Web3.HTTPProvider(node_url))

# verify the connection is successful
if web3.isConnected():
    print("Connection Successful")
else:
    print("Connection Failed")

# reconstruct contract in python
router_address = "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D"
uniswap_abi = "[{"inputs":[{"internalType":"address","name":"_factory","type":"address"},{"internalType":"address","name":"_WETH","type":"address"}],"stateMutability":"nonpayable","type":"constructor"},{"inputs":[],"name":"WETH","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"tokenA","type":"address"},{"internalType":"address","name":"tokenB","type":"address"},{"internalType":"uint256","name":"amountADesired","type":"uint256"},{"internalType":"uint256","name":"amountBDesired","type":"uint256"},{"internalType":"uint256","name":"amountAMin","type":"uint256"},{"internalType":"uint256","name":"amountBMin","type":"uint256"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"addLiquidity","outputs":[{"internalType":"uint256","name":"amountA","type":"uint256"},{"internalType":"uint256","name":"amountB","type":"uint256"},{"internalType":"uint256","name":"liquidity","type":"uint256"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"token","type":"address"},{"internalType":"uint256","name":"amountTokenDesired","type":"uint256"},{"internalType":"uint256","name":"amountTokenMin","type":"uint256"},{"internalType":"uint256","name":"amountETHMin","type":"uint256"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"addLiquidityETH","outputs":[{"internalType":"uint256","name":"amountToken","type":"uint256"},{"internalType":"uint256","name":"amountETH","type":"uint256"},{"internalType":"uint256","name":"liquidity","type":"uint256"}],"stateMutability":"payable","type":"function"},{"inputs":[],"name":"factory","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountOut","type":"uint256"},{"internalType":"uint256","name":"reserveIn","type":"uint256"},{"internalType":"uint256","name":"reserveOut","type":"uint256"}],"name":"getAmountIn","outputs":[{"internalType":"uint256","name":"amountIn","type":"uint256"}],"stateMutability":"pure","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountIn","type":"uint256"},{"internalType":"uint256","name":"reserveIn","type":"uint256"},{"internalType":"uint256","name":"reserveOut","type":"uint256"}],"name":"getAmountOut","outputs":[{"internalType":"uint256","name":"amountOut","type":"uint256"}],"stateMutability":"pure","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountOut","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"}],"name":"getAmountsIn","outputs":[{"internalType":"uint256[]","name":"amounts","type":"uint256[]"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountIn","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"}],"name":"getAmountsOut","outputs":[{"internalType":"uint256[]","name":"amounts","type":"uint256[]"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountA","type":"uint256"},{"internalType":"uint256","name":"reserveA","type":"uint256"},{"internalType":"uint256","name":"reserveB","type":"uint256"}],"name":"quote","outputs":[{"internalType":"uint256","name":"amountB","type":"uint256"}],"stateMutability":"pure","type":"function"},{"inputs":[{"internalType":"address","name":"tokenA","type":"address"},{"internalType":"address","name":"tokenB","type":"address"},{"internalType":"uint256","name":"liquidity","type":"uint256"},{"internalType":"uint256","name":"amountAMin","type":"uint256"},{"internalType":"uint256","name":"amountBMin","type":"uint256"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"removeLiquidity","outputs":[{"internalType":"uint256","name":"amountA","type":"uint256"},{"internalType":"uint256","name":"amountB","type":"uint256"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"token","type":"address"},{"internalType":"uint256","name":"liquidity","type":"uint256"},{"internalType":"uint256","name":"amountTokenMin","type":"uint256"},{"internalType":"uint256","name":"amountETHMin","type":"uint256"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"removeLiquidityETH","outputs":[{"internalType":"uint256","name":"amountToken","type":"uint256"},{"internalType":"uint256","name":"amountETH","type":"uint256"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"token","type":"address"},{"internalType":"uint256","name":"liquidity","type":"uint256"},{"internalType":"uint256","name":"amountTokenMin","type":"uint256"},{"internalType":"uint256","name":"amountETHMin","type":"uint256"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"removeLiquidityETHSupportingFeeOnTransferTokens","outputs":[{"internalType":"uint256","name":"amountETH","type":"uint256"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"token","type":"address"},{"internalType":"uint256","name":"liquidity","type":"uint256"},{"internalType":"uint256","name":"amountTokenMin","type":"uint256"},{"internalType":"uint256","name":"amountETHMin","type":"uint256"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"},{"internalType":"bool","name":"approveMax","type":"bool"},{"internalType":"uint8","name":"v","type":"uint8"},{"internalType":"bytes32","name":"r","type":"bytes32"},{"internalType":"bytes32","name":"s","type":"bytes32"}],"name":"removeLiquidityETHWithPermit","outputs":[{"internalType":"uint256","name":"amountToken","type":"uint256"},{"internalType":"uint256","name":"amountETH","type":"uint256"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"token","type":"address"},{"internalType":"uint256","name":"liquidity","type":"uint256"},{"internalType":"uint256","name":"amountTokenMin","type":"uint256"},{"internalType":"uint256","name":"amountETHMin","type":"uint256"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"},{"internalType":"bool","name":"approveMax","type":"bool"},{"internalType":"uint8","name":"v","type":"uint8"},{"internalType":"bytes32","name":"r","type":"bytes32"},{"internalType":"bytes32","name":"s","type":"bytes32"}],"name":"removeLiquidityETHWithPermitSupportingFeeOnTransferTokens","outputs":[{"internalType":"uint256","name":"amountETH","type":"uint256"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"tokenA","type":"address"},{"internalType":"address","name":"tokenB","type":"address"},{"internalType":"uint256","name":"liquidity","type":"uint256"},{"internalType":"uint256","name":"amountAMin","type":"uint256"},{"internalType":"uint256","name":"amountBMin","type":"uint256"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"},{"internalType":"bool","name":"approveMax","type":"bool"},{"internalType":"uint8","name":"v","type":"uint8"},{"internalType":"bytes32","name":"r","type":"bytes32"},{"internalType":"bytes32","name":"s","type":"bytes32"}],"name":"removeLiquidityWithPermit","outputs":[{"internalType":"uint256","name":"amountA","type":"uint256"},{"internalType":"uint256","name":"amountB","type":"uint256"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountOut","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"swapETHForExactTokens","outputs":[{"internalType":"uint256[]","name":"amounts","type":"uint256[]"}],"stateMutability":"payable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountOutMin","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"swapExactETHForTokens","outputs":[{"internalType":"uint256[]","name":"amounts","type":"uint256[]"}],"stateMutability":"payable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountOutMin","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"swapExactETHForTokensSupportingFeeOnTransferTokens","outputs":[],"stateMutability":"payable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountIn","type":"uint256"},{"internalType":"uint256","name":"amountOutMin","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"swapExactTokensForETH","outputs":[{"internalType":"uint256[]","name":"amounts","type":"uint256[]"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountIn","type":"uint256"},{"internalType":"uint256","name":"amountOutMin","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"swapExactTokensForETHSupportingFeeOnTransferTokens","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountIn","type":"uint256"},{"internalType":"uint256","name":"amountOutMin","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"swapExactTokensForTokens","outputs":[{"internalType":"uint256[]","name":"amounts","type":"uint256[]"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountIn","type":"uint256"},{"internalType":"uint256","name":"amountOutMin","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"swapExactTokensForTokensSupportingFeeOnTransferTokens","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountOut","type":"uint256"},{"internalType":"uint256","name":"amountInMax","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"swapTokensForExactETH","outputs":[{"internalType":"uint256[]","name":"amounts","type":"uint256[]"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amountOut","type":"uint256"},{"internalType":"uint256","name":"amountInMax","type":"uint256"},{"internalType":"address[]","name":"path","type":"address[]"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"deadline","type":"uint256"}],"name":"swapTokensForExactTokens","outputs":[{"internalType":"uint256[]","name":"amounts","type":"uint256[]"}],"stateMutability":"nonpayable","type":"function"},{"stateMutability":"payable","type":"receive"}]"

uniswap_contract = web3.eth.contract(address=router_address, abi=uniswap_abi)


# define the sender address and prints the balance (in ETH)
sender_address = "YOUR_ADDRESS_HERE"
private_key = "YOUR_PRIVATE_KEY"
balance = web3.eth.get_balance(sender_address)
print("This address has:", web3.fromWei(balance, "ether"), "ETH")

# specify token to buy
token_to_buy = web3.toChecksumAddress("TOKEN_ADDRESS")

# specifty token to spend (WETH mainnet)
spend = web3.toChecksumAddress("0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2")

# get nonce for the sender address
nonce = web3.eth.getTransactionCount(sender_address)

start = time.time()  # start of the tx

# call solidity function
uniswap_tx = uniswap_contract.functions.swapExactETHForTokens(
    0, [spend, token_to_buy], sender_address, (int(time.time()) + 10000)
).build_transaction(
    {
        "from": sender_address,
        "value": web3.toWei(0.1, "ether"),
        "gas": 2000000,
        "gasPrice": web3.toWei("10", "gwei"),
        "nonce": nonce,
    }
)

# sign transaction
sign_tx = web3.eth.account.sign_transaction(
    uniswap_tx, private_key
)  # use the private key to sign the transaction

# send transaction
tx_hash = web3.eth.send_raw_transaction(sign_tx.rawTransaction)

# get transaction confirmation and print hash
print(web3.toHex(tx_hash))