Get Account data length in a Transaction with Solana Py

Question

I'm building a program to co-sign transaction on solana.

The sign mechanism works, but now I'm trying to extract the account data length from a transaction that I'm receiving, because I want to calculate the cost of creating the account.

I'm sending this transaction from the frontend to the backend to co-sign it:

await program.value.transaction.sendTweet(topic, content, {
        accounts: {
            author: wallet.value.publicKey,
            feePayer: company_account_pubkey,
            tweet: tweet.publicKey,
            systemProgram: web3.SystemProgram.programId,
        }
    });

The contract is:

#[derive(Accounts)]
pub struct SendTweet<'info> {
    #[account(init, payer = feePayer, space = 1372)]
    pub tweet: Account<'info, Tweet>,
    #[account(mut)]
    pub author: Signer<'info>,
    #[account(mut)]
    pub feePayer: Signer<'info>,
    #[account(address = system_program::ID)]
    pub system_program: AccountInfo<'info>,
}

#[account]
pub struct Tweet {
    pub author: Pubkey,
    pub timestamp: i64,
    pub topic: String,
    pub content: String,
}

So just looking at the contract I can understand that the space required will be 1372.

But my service will interact with a lot of other programs, so I want to be able to extract the account data length by the transaction that I'm receiving.

On solana py, I know that I can get the data with tx.instructions[0].data and I know that I can get the cost of rent with client.get_minimum_balance_for_rent_exemption(1372)

But I don't know how to extract the size of the account from the transaction itself.

What am I missing?

Answer 1

I don't think the size of the account is included in the transaction info. It might be buried in getTransaction return values somewhere, but most likely you have to make a getAccountInfo call which will include the data, and you can check the length of data returned by it.