Hey buynano,

interesting tutorial, was also looking into buying card sets with python right now. There's just two thing which are puzzling me a bit:

1

Add owner.key
Make a new file called owner.key and place your hive owner key for the wallet you want to use. This is your private key so don't share it with anyone and make sure it's not network accessible.

By owner key, do you mean the private owner key of the account ? Or the Private posting key ? Because for neither operation you need the owner key. Active and posting are more than enough.

2 Is there a reason you are using the transaction builder instead of the custom json function on the hive instance itself ?