Actually I worked out a simple way to do it. I imported the txt file into Excel then ran some functions to search for the sec entries (using ISNUMBER for those that are interested) then sorted the entries to list the sec cells together before cleaning the data of non key text using find/replace. Copied the cleaned up keys into electrum and voila, the bitcoin-containing keys were registered.

Unfortunately I am not a programmer, TheArchaeologist, so creating a script is beyond my ability. I was hoping there was an automated way someone had already created but it seems not.

Thanks for the link, PawGo. I did read that thread when i did my original research but it didn't have an obvious solution (most answers had downvotes) and, besides, the issue the OP had in that thread was a little different to mine (my issue is being able to mine the txt file to copy all private keys, his was about how to get the text file in the first place for multiple wallets).

Thanks for the offer. however extracting all the public keys represents the same problem for me. There are too many to manually extract and copy. I need a way of going through the text file and pulling out all the private keys so I can paste them en masse into the sweep field in Electrum. Any thoughts as to how I can do that?

Applying pywallet's dumpwallet command to my 2013 wallet.dat file to produce a text file yields hundreds of addr, pubbkey, reserve and sec paragraphs. I tried to pick some of the "sec" listings (which i understand are the private keys) at random and sweep them into electrum but only get a "no inputs found" error message which I assume means that the private key is invalid or contains no bitcoin. is there a clever way to find the private keys that contain bitcoin or to extract all the private keys from the text file? Or have I got the whole sweep concept completely wrong? I've checked the "defaultkey" which i understand is the master public key to confirm that the wallet still contains some bitcoin so know that there is a (very modest) amount of value locked away in it. TIA!