Here's the only thing I've found that might fit the definition of "library" for trading, and it's in Java:

https://github.com/timmolter/XChange

Even though it's in Ruby, I'm finding this post helpful as I've started writing my own arbitrage bot in Python.  If you're looking to include arbitration in your bot, it may prove of use:

http://www.kelvinjiang.com/2010/10/currency-arbitrage-in-99-lines-of-ruby.html

Here are a few implementations of the above algo in Python:

http://shriphani.com/blog/2010/07/02/bellman-ford-algorithms-applications-triangular-arbitrage/
https://github.com/mlbright/arbitrage

I know that you're not looking for an actual bot, but here's one specifically for arbitrage in Python that might help you with exchange APIs. It's even licensed MIT (thanks maxme!). It uses a brute force algo for arbitration, and I don't know enough about this to say whether or not it would be as effective as something like Bellman-Ford. 

https://github.com/maxme/bitcoin-arbitrage

I

Where are you in the US that you don't think we have double-digit inflation *right now*?  Have you audited all your basic expenses from year to year?  I have, and the rate is hovering above 10% for the past 2 years.  Why do people believe the official numbers when all they have to do is run a few calculations on Quicken to see that those numbers are ridiculously low?

Great, smart move to move all your bitcoins elsewhere temporarily.  I'm relieved you did that.

I think someone else is helping you right now via teamviewer but if not pm me and I'll see if I can help you sometime today or tomorrow.

Hi reg,

First, make a safe, secure backup of your wallet.dat.  This is absolute. Do that before anything, and even if something goes wrong you'll still have your coins.

In my opinion, the simplest option is just to create a symbolic link to the upgraded bitcoin-qt client.  This is like a Windows shortcut.  Assuming you put it in a directory called 'Documents' in your home directory, you want to run this command in your terminal (ctrl-T usually).  If you use Ubuntu or Linux Mint, you'd run:

sudo rm /usr/bin/bitcoin-qt
sudo ln -s ~/Documents/bitcoin-0.8.1-linux/bin/64/bitcoin-qt /usr/bin/bitcoin-qt

Otherwise, you'd switch to root and then run the two command above without the sudo in front.  Make sure the directory names above match exactly your actual directory names (e.g., if you renamed bitcoin directory you'd need to adjust the directory name accordingly).

You'll need to change the 64 in the command above to a 32 if your os is 32-bit.  You can check this by running:

uname -p

If it says "x86_64" or "ia64", you need "64" but if it says anything else, like "i686" or "i386", then you need "32".

Normally, you'd want to move the new bitcoin app to another location (like /opt) but for the sake of simplicity just keep it in the Documents directory unless you feel comfortable moving it. If you do move it, you'll need to relink it using the commands above, but with the new directory.

Once you do this, any menu shortcuts you have to bitcoin should run the updated version.  You'll need to delete all the files from your .bitcoin hidden directory except your wallet.dat before you run the updated client.  The safest way to do that is to make sure you've backed up (copied) your wallet.dat to another directory, then delete all the files in the .bitcoin directory, then copy the wallet.dat back in.  Use the GUI file manager for this if you feel more comfortable.  The new version of bitcoin will still look for your wallet in the same default location (the ls -".bitcoin" directory).  If you don't know how to do this, or don't feel comfortable doing it, then post a response and me or someone else will help.

Good luck!  And just know that as long as you have the wallet.dat backed up, there's almost always a way to get to your coins if something goes wrong (nothing should go wrong if you follow the directions above).  So make sure you've securely backed up wallet.dat before any of this, and make sure it's a new backup.

Also, bitstamp, an exchange that caters to Europeans dealing in the dollar, is leading the charge.  More support for this hypothesis that Europe is getting on board.

Perhaps those that do business in Euros, but many of those Europeans who use USD may prefer bitstamp.  I don't have a preference (although I'm impressed with bitstamp's design), just floating a hypothesis.

Or it could be the Europeans entering the Bitcoin economy, since bitstamp caters to Europe with its Sepa deposits. 

Don't look toward Cyprus in the coming days.  Look toward Bitcoin adoption in Spain and Italy.  That's where the real impact of the situation in Cyprus will land.

I agree completely.  Is a custom Linux distro the best solution?  It may well be, perhaps booting into a kiosk app.  Are you imagining people would use it to create a wallet to store funds, perhaps on an external USB with a paper wallet backup?  And then maybe boot into the distro whenever they need to top up their everyday wallet, whether that's Electrum, the official client, blockchain.info, or some other client.  This working wallet would only contain the funds they could afford to lose.

There was LinuxCoin, which was based on debian.  As far as I know, it was last updated in 2011 so it's now fairly obsolete.  I used it back then, and it's nice but not targeted toward non-tech folks.  However, I had missed BitSafe, mentioned in this thread.  I'll have to look into it, looks impressive.  Wonder if the GUI is friendly enough for non-Linux people.

I'm imagining something akin to a kiosk app that the distro would boot into, which would have simple buttons/menus for doing things like creating addresses, backing up, sending, paper wallets, etc.  Kivy is a good Python framework for creating kiosk apps that runs on Linux and Android (and other platforms).

I think that in addition to Linux, it's worth considering Android for this kind of OS that would boot into a single app, using bitcoinj.

I've got a lot of Linux experience and am comfortable with Kivy, and other GUI toolkits as well.  Unfortunately, I'm also quite booked for the next few weeks.  Nonetheless, I agree this is something that needs to be done and I'd like to contribute whatever I can, whether that's bash or Python scripts or something else.  It may be that Bitsafe fulfills our needs, and just needs to promoted among Bitcoin novices.

Great, I'm glad.  For the reference of future readers, the fact that you were able to retrieve them using Mac TimeMachine means that if this approach hadn't worked, someone would likely have been able to guide you to get your Bitcoins through using something like pywallet to dump the keys.  So if you "loose" Bitcoins during an upgrade, they're almost certainly still there, and if you remain calm like marra you should be able to retrieve them.

In any case, glad you got your coins back marra.   Well done.

In the future, all of this will be easier...  Getting better by the day.

How did it go?

No, it certainly doesn't require 2 exchanges.  There are thousands of people doing cross-currency arbitrage as we write this.  See: http://en.wikipedia.org/wiki/Triangular_arbitrage  This can be done in a single exchange.

And cross-currency arbitrage is getting quite popular in exchanges with several virtual and fiat currencies, like vircurex and btc-e.

A market is not synonymous with "an exchange".  Each exchange has multiple markets (usually): USD-BTC, EUR-BTC, LTC-BTC, etc.

Well, you could spend money on bitcoin, and if you restored a backup from 2 weeks ago, and if bitcoin-qt hadn't yet caught up with the blockchain, it would still show your spent balance.  But you couldn't get any confirmations if you tried to spend them.  So this is not really a definitive restoration until the old client has caught up with the blockchain.  So make sure the client is caught up with the blockchain before you try to spend them (make sure it no longer says "unsynchronized").

Good luck.

Yes, theoretically.  But I'm not very familiar with blockchain.info  I'd download the very latest official bitcoin-qt client (8.1), not earlier versions since there was a change in database backends that could be causing your problem.  And then just >bitcoin-qt -datadir=/folder/with/wallet.dat -rescan  

First with your regular wallet, and if that doesn't work with your backup.  It will take a while but please let us know how it goes.

PS: Make sure your antivirus and/or firewall are not blocking bitcoin.

Yes, totally, my bad.  If there are more than 100 transactions since you made your backup, you need to use the latest one.  

But the fact that this happened right around your upgrade makes me think that you've encountered a (very panic inducing) bug that can be resolved if you keep your cool.

OK, that's a good sign.  I think your coins may still be there.  Don't panic.

Have you tried downloading the latest client (8.1) then running if from the command line like this: bitcoin-qt -datadir=/folder/with/wallet.dat -rescan

It will take a while, but do that first with your backed-up wallet, then with your regular one.

It would be unheard of for the blockchain to have been manipulated, and if that happened much larger accounts than yours would be affected.

EDIT: Just to be sure, where did you download your upgrade from?

You're correct, Ripple transactions are virtually instant.  It appears that Bitstamp is having to manually clear transactions from time to time.  Perhaps because their hotwallet runs out.  Bitstamp devs, any comment?

They just sorted out a similar problem with me (for about 3 btc), crediting my account for a missing Ripple deposit just hours after contacting them at their support e-mail.  Contact them directly at their support e-mail with the transaction id and they'll almost certainly credit your account.  It's 2 a.m. in Europe now, which is likely why there is no response.

Thank you.  Very well done summary of the current state of Litecoin.  Maybe this can become a tradition?  Day after St. Paddy's?

Congrats.  It's good to see you all back.  You were always my favorite exchange.  Now, if I had only kept all the btc I bought from tradehill...