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Monitor transfers using Python

In this tutorial, you'll monitor transfers to an Ethereum account using the Web3 Python library.

Prerequisites​

  • Pip installed

Steps​

1. Create a project directory​

Create a new directory for your project. This can be done from the command line:

mkdir monitorTransfer

Change into the new directory:

cd monitorTransfer

2. Install required packages​

Install the web3.py package:

pip install web3

3. Create a script file​

Create a file called monitorTransactions.py. At the top of file, add the following lines to import the web3.py library:

from web3 import Web3
import time

4. Connect to Infura​

Connect to the Infura endpoint and the address of the account:

infura_url = "https://mainnet.infura.io/v3/<YOUR-API-KEY>"
account = "<YOUR-PUBLIC-ADDRESS>"
web3 = Web3(Web3.HTTPProvider(infura_url))
warning

Replace <YOUR-API-KEY> with your Infura API key and <YOUR-PUBLIC-ADDRESS> with the Ethereum account you want to monitor.

5. Set the function​

Create a function to check new transactions for the account defined in step 3 and retrieves the details for the transaction:

def watch():
  while True:
    block = web3.eth.get_block("latest")
    print("Searching in block " + str(block.number))

    if block and block.transactions:
      for transaction in block.transactions:
        tx_hash = transaction.hex()  # the hashes are stored in a hexBytes format
        tx = web3.eth.get_transaction(tx_hash)
        if tx.to is not None:
          if tx.to == account:
            print("Transaction found in block {} :".format(block.number))
            print({
              "hash": tx_hash,
              "from": tx["from"],
              "value": web3.fromWei(tx["value"], "ether")
            })
    time.sleep(5)

watch()

6. Check for confirmations​

Exchanges often wait until a deposit has reached a certain number of confirmations before processing the new transaction. The number of confirmations is the number of blocks that have passed since the transaction was included onchain. By checking that a transaction has reached the specified number of confirmations, the exchange can be confident that this transaction is final and they can process the deposit.

Create a function to determine the number of confirmations for the transaction:

def confirmations(tx_hash):
  tx = web3.eth.get_transaction(tx_hash)
  return web3.eth.block_number - tx.blockNumber

You can then call the function using something similar to:

print(confirmations(tx_hash))

7. Run the script​

Run the script using the following command:

python3 monitorTransactions.py

Complete code overview​

from web3 import Web3
import time

infura_url = "https://mainnet.infura.io/v3/<YOUR-API-KEY>"
account = "<YOUR-PUBLIC-ADDRESS>"
web3 = Web3(Web3.HTTPProvider(infura_url))

def confirmations(tx_hash):
  tx = web3.eth.get_transaction(tx_hash)
  return web3.eth.block_number - tx.blockNumber

def watch():
  while True:
    block = web3.eth.get_block("latest")
    print("Searching in block " + str(block.number))

    if block and block.transactions:
      for transaction in block.transactions:
        tx_hash = transaction.hex()  # the hashes are stored in a hexBytes format
        tx = web3.eth.get_transaction(tx_hash)
        if tx.to is not None:
          if tx.to == account:
            print("Transaction found in block {} :".format(block.number))
            print({
              "hash": tx_hash,
              "from": tx["from"],
              "value": web3.from_wei(tx["value"], "ether")
            })
    time.sleep(5)

watch()
# print(confirmations("0x0d40d60e118e9e1f61c2baa2252cc5f8b8ed491c885ec35db6fd6cfc8589c1a7"))
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