How do I automatically update the latest block number and pending txns in my app?

Question

I wish to make a simple application using KivyMD. I want to display the latest block and pending txns on the ethereum blockchain and have it update automatically with every new block. I'm using infura url and web3.py.

pending_block = web3.eth.getBlock(block_identifier='pending', full_transactions=True)
pending_transactions = pending_block['transactions']

What do I do to make the app automatically get this every time a new block originates? Listeners? Websockets? Or use a while loop that sleeps for a specified time and calls a function to fetch the latest data?

Answer 1

You need to listen to blockchain events. From Web3js documentation:

var subscription = web3.eth.subscribe('newBlockHeaders', function(error, result){
    if (!error) {
        console.log(result);

        return;
    }

    console.error(error);
})
.on("connected", function(subscriptionId){
    console.log(subscriptionId);
})
.on("data", function(blockHeader){
    console.log(blockHeader);
})
.on("error", console.error);

// unsubscribes the subscription
subscription.unsubscribe(function(error, success){
    if (success) {
        console.log('Successfully unsubscribed!');
    }
});

Answer 2

Maybe this code help you. It contains recursive function.

def checkBlockNumber(blockNumber = None):
    if blockNumber:
        if blockNumber == w3.eth.get_block_number():
            time.sleep(1)
            checkBlockNumber(blockNumber)
    else:        
        return w3.eth.get_block_number()

while True:
    block_number = checkBlockNumber()
    print(block_number)
    checkBlockNumber(block_number)