Python Quickstart (web3.py)

Connect to Sei from Python using web3.py — read chain data, then sign and broadcast transactions against the Sei EVM JSON-RPC.

Python Quickstart (web3.py)

Sei is fully EVM-compatible, so any standard Ethereum client works — including Python’s web3.py. This guide connects to Sei from a Python script, reads chain data with no credentials, then signs and broadcasts a transaction.

Install

We recommend an isolated virtual environment:

python3 -m venv venv
source venv/bin/activate          # Windows: venv\Scripts\activate
pip install web3

Reading Chain Data

This is the first milestone — it needs no private key.

from web3 import Web3

w3 = Web3(Web3.HTTPProvider("https://evm-rpc.sei-apis.com"))

# Any valid Sei EVM address — swap in your own
address = "0x0000000000000000000000000000000000000000"

print("Connected:", w3.is_connected())
print("Chain ID:", w3.eth.chain_id)                                  # 1329 on mainnet
print("Latest block:", w3.eth.block_number)
print("Balance (SEI):", w3.from_wei(w3.eth.get_balance(address), "ether"))
print("Nonce:", w3.eth.get_transaction_count(address))

You’re done when you see:

Connected: True
Chain ID: 1329
Latest block: 148203117
Balance (SEI): 12.5
Nonce: 7

Values are illustrative — your block number, and the queried address’s balance and nonce, will differ. The chain ID is always 1329 on mainnet (1328 on the atlantic-2 testnet).

Sending a Transaction

Next step — this requires a funded account. Get testnet SEI from the faucet, then build, sign locally, and broadcast with eth_sendRawTransaction. Public RPC endpoints don’t manage accounts, so you sign the transaction yourself rather than relying on node-managed accounts.

import os
from web3 import Web3

# atlantic-2 testnet
w3 = Web3(Web3.HTTPProvider("https://evm-rpc-testnet.sei-apis.com"))

account = w3.eth.account.from_key(os.environ["SEI_PRIVATE_KEY"])

tx = {
    "to": "0xRecipient",
    "value": w3.to_wei(0.001, "ether"),
    "nonce": w3.eth.get_transaction_count(account.address),
    "chainId": w3.eth.chain_id,
    "type": 2,  # EIP-1559
    "maxPriorityFeePerGas": w3.to_wei(1, "gwei"),
    "maxFeePerGas": w3.eth.gas_price * 2 + w3.to_wei(1, "gwei"),
}
tx["gas"] = w3.eth.estimate_gas(tx)  # always estimate rather than hard-coding

signed = w3.eth.account.sign_transaction(tx, account.key)
tx_hash = w3.eth.send_raw_transaction(signed.raw_transaction)

receipt = w3.eth.wait_for_transaction_receipt(tx_hash)
print("Mined in block:", receipt.blockNumber)  # final immediately — Sei has instant finality

Never hard-code or commit a private key. Load it from an environment variable or a secrets manager, and use a dedicated throwaway key funded with only what you need.

signed.raw_transaction is the attribute name in web3.py v7+. On web3.py v6 it is signed.rawTransaction.

Reading a Contract

abi = [{
    "constant": True,
    "inputs": [{"name": "owner", "type": "address"}],
    "name": "balanceOf",
    "outputs": [{"name": "", "type": "uint256"}],
    "stateMutability": "view",
    "type": "function",
}]

token = w3.eth.contract(address="0xTokenAddress", abi=abi)
print(token.functions.balanceOf(address).call())

Next Steps

• viem Quickstart — the TypeScript/Node.js equivalent
• ethers v6 Quickstart — TypeScript with ethers
• Network information — RPC endpoints, chain IDs, and explorers
• Faucet — get testnet SEI