How to get transaction details from filter in web3.py

Question

I am developing a software that listens for pending transactions.

...
web3 = Web3(HTTPProvider(cfg.eth_node_url))
web3_pending_filter = web3.eth.filter('pending')
transaction_list = web3.eth.getFilterChanges(web3_filter.filter_id)
...

In documentation of web3.py here is written that filter's getFilterChanges method should return transaction objects (list of dictionaries), but I am receiving list of hashes only. How can I get list of 'full' transactions from filter?

Answer 1

The docs you linked to are showing examples from filtering for events. Since you are filtering for pending transactions, it will be a bit different.

When listing pending transactions, you only get the transaction hashes, as specified in the json-rpc spec:

For filters created with eth_newPendingTransactionFilter the return are transaction hashes (DATA, 32 Bytes), e.g. ["0x6345343454645..."].

So you would get the list of transaction details using something like:

transaction_hashes = web3.eth.getFilterChanges(web3_filter.filter_id)
transactions = [web3.eth.getTransaction(h) for h in transaction_hashes]

Answer 2

You can get transaction details via

web3.eth.getTransaction(txnHash) 

If no transaction for the given hash can be found, then this function will instead return None. https://web3py.readthedocs.io/en/stable/examples.html#looking-up-transactions

In the following paragraph in the above documentation, you can check if the transaction has been mined(included into the blockchain) or not:

web3.eth.getTransactionReceipt(txnHash)

If the transaction has not yet been mined then this method will return None.