What's the difference between transact and buildTransaction?

Question

I noticed that there are two options to create a transaction / call a state-changing function.

In the first one we receive the transaction hash (tx_hash) by building the transaction, signing the transaction using our private key, sending raw transaction, and waiting for the receipt:

simple_storage = w3.eth.contract(address=tx_receipt.contractAddress, abi=abi)

store_tx = simple_storage.functions.store(_favoriteNumber=12).buildTransaction(
    {
        "from": my_account,
        "chainId": network_id,
        "nonce": w3.eth.get_transaction_count(account=my_account),
    }
)
signed_tx = w3.eth.account.sign_transaction(store_tx, private_key=private_key)
tx_hash = w3.eth.send_raw_transaction(signed_tx.rawTransaction)
tx_receipt = w3.eth.wait_for_transaction_receipt(tx_hash)

and in the second option we simply use the transact() function to receive our tx_hash:

tx_hash = simple_storage.functions.store(_favoriteNumber=12).transact(
    {
        "from": my_account,
        "chainId": network_id,
        "nonce": w3.eth.get_transaction_count(account=my_account),
    }
)

What is the difference between these two?

Answer 1

The second one requires a middleware to sign the transaction with the private keys (it could be a web3 provider like Metamask, a hardware wallet service, etc).

If you use the same private key the resulting transaction should be indistinguishable.