How To Use JSON-RPC With Web3.py

JSON-RPC With Web3.py

First off, what the heck IS Web3.ps? Web3.py is a python library for interacting with Ethereum. Its API is derived from the Web3.js Javascript API.

In this article, we're going to talk about how to use it with your Ethereum node, with a few practical examples.

Step one

Install:

Web3.py can be installed (preferably in a virtualenv) using pip as follows:

$ pip install web3

Step two

python3 script.py

web3 = Web3(HTTPProvider('https://ethshared.bdnodes.net')) 

print(web3.eth.blockNumber) 

web3 = Web3(HTTPProvider('https://ethshared.bdnodes.net'))

print(web3.eth.gasPrice)

Send Ether to another account:

Python3 Code examples

import sys

from web3: import Web3, HTTPProvider

Connect to the Blockdaemon Ethereum endpoint

w3 = Web3(HTTPProvider('https://ethshared.bdnodes.net'))

 Get the sender's private key

senderKey = input("Enter sender private key (e.g. export from MetaMask): ")

try:

senderAccount = w3.eth.account.privateKeyToAccount(senderKey)

exception:

print("ERROR: Not a valid private key")

sys.exit(1)

 Get the receiver's address

receiver_address = input("Enter receiver address: ")

if not Web3.isAddress(receiver_address):

print("ERROR: Not a valid address")

sys.exit(1)

 Create the transaction

transaction = {

   'to': receiver_address,
 
    'value': 1, # Sending 1 wei

    'gas': 90000, # The default in geth
 
     'gasPrice': w3.eth.gasPrice, # Use the value determined by the node
 
     'nonce': w3.eth.getTransactionCount(senderAccount.address) # Get correct transaction nonce for sender from the node
 }

 Sign the transaction

signed = w3.eth.account.signTransaction(transaction, senderAccount.privateKey)

 Send it!

txHash = w3.eth.sendRawTransaction(signed.rawTransaction)
print(f"Succesfully sent transaction {Web3.toHex(txHash)}")

 A video walkthrough of using a smart contract with Ethereum

 Helpful docs:

https://web3py.readthedocs.io/en/stable/web3.eth.account.html

https://eth-account.readthedocs.io/en/latest/

 More Reference articles:

Working with local private keys

Some Common Uses for Local Private Keys

A common reason to work with local private keys is to interact with a hosted node.

Some common things you might want to do with a Local Private Key are:

• Sign a Transaction
• Sign a Contract Transaction
• Sign a Message
• Verify a Message