down vote
Beside that I don't understand your problem with PyWaller, like Eyal suggests, you can use the standard Bitcoin software for this as well, although this method will be a little more time-consuming.
I suggest doing the following for every wallet.dat file you have:
Backup your current wallet.dat file.
Copy the old wallet.dat to your Bitcoin directory.
Open up a terminal and run the bitcoind daemon:
bitcoind -daemon
Retrieve a list of all the addresses in the wallet:
bitcoind listaddressgroupings
For every address you want the private key from, dump it:
bitcoind dumpprivkey <bitcoinaddress>
Stop the daemon before changing the wallet.dat file:
bitcoind stop
