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January 29, 2013

Using Mechanical Turk to build a library of Grocery Cards

by e1ven

Envelopes

Earlier this year, I wanted to add the ability to generate and display barcodes as part the Savingstar iPhone app, similar to Loyalty card wallets.
We’re already storing loyalty card numbers of over a million users in order to process their coupons – It seemed like regenerating these into scannable barcodes should be simple enough.
For stores with a scanner that can read a phone (an increasing number), this is a lot more convenient.

Looking over the various card ranges, they fell into a few formats- EAN-13, UPC, etc.

Luckily, there is a library which can easily write these, and easy to use python bindings in order to use them.

Barcode

After a few trials however, I ran into a small issue-

The numbers in the barcode don’t always match up with the printed card number!

Often there is a prefix/postfix on the number, in addition to the checkdigits for UPCs.
After thinking about it for a while, I realized I could reverse engineer the formats, but I’d need cards. Lots of cards.

I turned to Mechanical Turk.

Getting Cards

I posted several jobs, each time asking people to mail me loyalty cards.
Because I needed to match the cards to a something digital to approve/deny them on Mechanical Turk, generated hundreds of random strings, and assigned one to each user.
I then asked each user to then write their particular random string on the envelope; When I received the envelope, I could match it up and give them credit for the job.

And we got cards! Hundreds of beautiful cards, dozens of cards in each of the ranges I needed.
People from around the US and Canada send cards from every major chain in the US.

The biggest downsize to this method is that there is a built in lag.. So even after I had enough cards for each certain chains, and pulled the listing, I still received loads of cards that had already been mailed 😉

In App

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