Python Quickstart (web3.py)

Sei is fully EVM-compatible, so any standard Ethereum client works with it, including Python’s web3.py. In this guide, you connect to Sei from a Python script and read chain data without credentials. Then you sign and broadcast a transaction.

Install

Use 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 does not need a 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 are done when you see:

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

The exact values are illustrative. Your block number will differ, and so will the balance and nonce of the queried address. The EVM chain ID is always 1329 on Sei Mainnet and 1328 on Sei Testnet.

Try it live

web3.py sends plain JSON-RPC requests internally. These snippets send the same reads to Sei Mainnet, so you do not need Python to run them.

Sending a transaction

This next step requires a funded account. Get testnet SEI from the faucet. Then build the transaction, sign it locally, and broadcast it with eth_sendRawTransaction. Public RPC endpoints do not manage accounts, so you sign the transaction yourself instead of relying on node-managed accounts.

import os
from web3 import Web3

# Sei 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. Use a dedicated throwaway key that holds only the funds you need.

In web3.py v7+, the attribute name is signed.raw_transaction. In 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 and Node.js equivalent
ethers v6 Quickstart: TypeScript with ethers
Network information: RPC endpoints, chain IDs, and explorers
Faucet: get testnet SEI

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Python Quickstart (web3.py)

Install

Reading chain data

Try it live

Sending a transaction

Reading a contract

Next steps

​Install

​Reading chain data

​Try it live

​Sending a transaction

​Reading a contract

​Next steps

Install

Reading chain data

Try it live

Sending a transaction

Reading a contract

Next steps