OP have yet to answer the main question (which asked by me and few other member)
It seems a bit difficult to find out how many bitcoins a specific wallet contains.
How does people keep track of it? Manually??
This is clearly XY problem. What are you trying to achieve by reading content of a wallet file?
If you tell us what you're trying to solve or at least what kind of wallet you're trying to read, you'd get clear answer.
Otherwise, you could probably use PyWallet to dump out the addresses in a wallet.dat file and then run a script that queries a block explorer API to see what the current balance of those addresses is... I'm not aware of any "ready to go"/"off the shelf" scripts that do this at present.
At this point, I tend to believe he's trying to access the funds inside those wallets but is having a hard time cracking it.
If it's true, then OP is more likely to ask how to crack/bruteforce bitcoin wallet.