Uniswap v4 Python Token Swapper – Universal Router

A user-friendly Python script that demonstrates how to execute SWAP_EXACT_IN (Exact Input) swaps on Uniswap v4 Universal Router across various L2 networks, leveraging the uniswap-universal-router-decoder library.

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Features

• Supports Uniswap v4 Universal Router.
• Works with both v3 and v4 (untested) pools.
• Auto-selects the router address based on the connected chain (Base, Optimism, Polygon, Arbitrum, Ethereum).
• Permit2 integrated for simplified token approvals.
• Checks & Cancels stuck transactions automatically.
• Written in Python using web3.py, eth_account, and uniswap-universal-router-decoder.

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Installation

1. Clone This Repo (or download the script directly)
2. Install Dependencies:

pip install web3 eth_account eth_abi uniswap-universal-router-decoder

3. (Optional) Create a Virtual Environment

python -m venv venv
source venv/bin/activate  # On Linux/Mac
# or venv\Scripts\activate on Windows

4. Ensure You Have Python 3.8+

python --version

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Quick Start

from web3 import Web3
from uniswap_universal_router import Uniswap  # or whatever you name this script

# 1. Connect to an L2 or mainnet RPC
provider_url = "https://base-mainnet-rpc.example"  # Replace with your provider
web3 = Web3(Web3.HTTPProvider(provider_url))

# 2. Prepare wallet credentials
wallet_address = "0xYOUR_WALLET_ADDRESS"
private_key = "YOUR_PRIVATE_KEY"  # Keep secret!

# 3. Instantiate the Uniswap helper
uniswap = Uniswap(
    wallet_address=wallet_address,
    private_key=private_key,
    provider=provider_url,  # Used to auto-detect chain
    web3=web3
)

# 4. Perform a swap (SWAP_EXACT_IN)
# Example: Swap 1 tokenIn -> tokenOut at 0.3% fee in a v3 pool
amount_in_wei = web3.to_wei(1, 'ether')

try:
    tx_hash = uniswap.make_trade(
        from_token="0xTOKEN_IN_ADDRESS",
        to_token="0xTOKEN_OUT_ADDRESS",
        amount=amount_in_wei,
        fee=3000,         # e.g., 3000 for a 0.3% Uniswap V3 pool
        slippage=0.5,     # non-functional right now. 0.5% slippage tolerance
        pool_version="v3"  # can be "v3" or "v4"
    )
    print(f"Swap transaction sent! Tx hash: {tx_hash.hex()}")
except Exception as e:
    print(f"Swap failed: {e}")

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How It Works

1. Router Detection: Based on your provider_url, the script automatically selects the correct Uniswap v4 Universal Router address for Base, Optimism, Polygon, Arbitrum, or Ethereum.
2. Permit2 Approvals: Checks and (if necessary) approves the Uniswap Permit2 contract before swapping, minimizing repeated approvals.
3. Transaction Construction: Leverages uniswap-universal-router-decoder to encode swap calls. Handles v3_swap_exact_in or v4_swap logic depending on pool_version.
4. Transaction Submission: Signs and sends a type=2 (EIP-1559) transaction with dynamic gas.
5. Stuck Transactions Check: If a nonce is stuck, attempts to cancel it by sending a 0-value tx with a higher gas.
6. Stuck but not visible Transaction?: Uncomment nonce, write in specific nonce that is the problem and it will attempt to cancel it by sending a 0-value tx with a higher gas.

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Code Overview

• Uniswap class
  • __init__: Initializes Web3, detects chain, sets up router.
  • approve_permit2: Approves the Permit2 contract with infinite allowance.
  • check_permit2_allowance: Checks if there’s already sufficient allowance.
  • create_permit_signature: Generates a Permit2 signature for the swap.
  • make_trade: The main function for executing swaps.
  • check_for_stuck_transactions: Detects if a transaction nonce is stuck in pending.
  • cancel_transaction: Attempts to cancel a stuck transaction by overriding its nonce.
  • calculate_gas_parameters: Estimates baseFee and priorityFee, calculates total cost.

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Supported Chains (with Addresses)

Chain	Router Address
Ethereum	0x66a9893cc07d91d95644aedd05d03f95e1dba8af
Base	0x6ff5693b99212da76ad316178a184ab56d299b43
Optimism	0x851116d9223fabed8e56c0e6b8ad0c31d98b3507
Polygon	0x1095692a6237d83c6a72f3f5efedb9a670c49223
Arbitrum	0xa51afafe0263b40edaef0df8781ea9aa03e381a3

Note: These addresses may change if Uniswap deploys updates.

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Troubleshooting

• Web3 Connection Failed: Make sure your RPC URL is correct and the network is live.
• Insufficient Balance or Allowance: Ensure you have enough tokens/ETH for gas and correct Permit2 approvals.
• Stuck Nonce: The script automatically checks and attempts to cancel.
• Unsupported Chain: Add your chain to ROUTER_ADDRESSES or specify ethereum.

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Disclaimer

• Use at your own risk – This is experimental code for demonstration purposes.
• Always test on a testnet or with small amounts before using in production.
• Make sure you keep your private keys secure.

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Contributing

Pull requests are welcome! If you want to expand functionality or fix issues, feel free to open a PR.

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License

This project is released under the MIT License.

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Credits

• Built on top of uniswap-universal-router-decoder for encoding/decoding logic.
• Thanks to Web3.py and Eth Account.