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Author Topic: Help querying blockchain API  (Read 925 times)
jackpf (OP)
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February 20, 2014, 09:43:47 PM
 #1

Hi all,

I need a bit of help using the blockchain API. I am querying it like this: https://blockchain.info/address/18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp?format=json
But the transaction results seem skewed, for example the transaction hash and result for the first few transactions are:
fcd4187e00b13575fd7859d2530bb90596e3f2c73063d9b959d37706447c1d95: 0
516de45c60a4ec58cb57b6d5fa2f6fabc454a25db29c0970d05366c9f99795d3: -410000
a623c4c5bc598cd8214196262905583eff7cb124b618aa72940d029f25c07b00: 30000000

Whereas if you look at the actual address page: https://blockchain.info/address/18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp
It should be more like this:
fcd4187e00b13575fd7859d2530bb90596e3f2c73063d9b959d37706447c1d95: -410000
516de45c60a4ec58cb57b6d5fa2f6fabc454a25db29c0970d05366c9f99795d3: 30000000
a623c4c5bc598cd8214196262905583eff7cb124b618aa72940d029f25c07b00: 10000000

Why is the first result always 0, which then offsets the rest of the results to be incorrect? Is this a bug in the api or am I doing it wrong?

Any help is much appreciated.

Thank you,
jackpf
DannyHamilton
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February 21, 2014, 12:20:30 AM
 #2

What is the "result" value supposed to represent?

I don't see it on the API documentation page:
https://blockchain.info/api/blockchain_api
jackpf (OP)
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February 21, 2014, 12:48:38 AM
 #3

I believe it is the amount of btc given/taken from the address for a given transaction. If you look at the "single address" API call in that documention, in the response you see:
"tx":[--Array of Transactions--]

In this array is a set of transactions for the given address.

As you can see in this screenshot:
https://www.dropbox.com/s/1j4rwqhosdtoghq/Screenshot_2014-02-21-00-43-48.png
It is (almost) the same as the blockchain address page:
https://blockchain.info/address/18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp

However, in the first screenshot the first result is 0, and every transaction hash has the next transaction's value, if that makes sense.
And in the json, I can clearly see the first transaction has result: 0, so I don't think I am querying it wrong. Is this a bug in their API?

Thanks for the response,
jackpf
jackpf (OP)
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February 21, 2014, 02:21:07 PM
 #4

Polite bump, really need help with this! Don't understand why the API is returning these values Sad
DannyHamilton
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February 21, 2014, 04:17:25 PM
 #5

I believe it is the amount of btc given/taken from the address for a given transaction. If you look at the "single address" API call in that documention, in the response you see:
"tx":[--Array of Transactions--]

In this array is a set of transactions for the given address.

As you can see in this screenshot:
https://www.dropbox.com/s/1j4rwqhosdtoghq/Screenshot_2014-02-21-00-43-48.png
It is (almost) the same as the blockchain address page:
https://blockchain.info/address/18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp

However, in the first screenshot the first result is 0, and every transaction hash has the next transaction's value, if that makes sense.
And in the json, I can clearly see the first transaction has result: 0, so I don't think I am querying it wrong. Is this a bug in their API?

Thanks for the response,
jackpf

It may be a bug in the API.  As I said, the "result" label:value pair is not in the documentation for the API.  An [--Array of Transactions--] should be a set of "single transactions".  Take a look at the "single transaction" API call in that documentation, you'll see that "result" isn't in the specified output.

Perhaps a more reliable way to determine how much was spent and/or received would be to add up the inputs and/or outputs.

For example you can see in this txs array element:

Code:
{
    "result":0,
    "block_height":286985,
    "time":1392950149,
    "inputs":[
        {
            "prev_out":{
                "n":12,
                "value":100000000,
                "addr":"1PyZ3PT8bv6dy4HcNzX2ba2zQm1sAgmEqE",
                "tx_index":113566887,
                "type":0
            }
        }
    ],
    "vout_sz":2,
    "relayed_by":"178.63.63.214",
    "hash":"5f9b073f26a3b7b86d44b6aed164d7973867e1ed5388ad327e02ee95232e8123",
    "vin_sz":1,
    "tx_index":113580991,
    "ver":1,
    "out":[
        {
            "n":0,
            "value":10000000,
            "addr":"18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp",
            "tx_index":113580991,
            "type":0
        },{
            "n":1,
            "value":89990000,
            "addr":"1LWxoxVx4dC5FrwmWiVL3uCTS5frj8sbGv",
            "tx_index":113580991,
            "type":0
        }
    ],
    "size":226
},

That there are no "inputs" array elements with a "prev_out" that was sent to an "addr" of 18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp.  Therefore nothing is "spent"

Meanwhile there is a single "out" array element that was sent to an "addr" of 18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp. That one array element has a "value" of 10000000.  Therefore 10000000 satoshis (0.1 BTC) were "received" at that address with this transaction.

Meanwhile you can see in this txs array element:

Code:
{
    "result":10000000,
    "block_height":286604,
    "time":1392772520,
    "inputs":[
        {
            "prev_out":{
                "n":1,
                "value":4720000,
                "addr":"18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp",
                "tx_index":113271796,
                "type":0
            }
        }
    ],
    "vout_sz":2,
    "relayed_by":"176.9.104.178",
    "hash":"fcd4187e00b13575fd7859d2530bb90596e3f2c73063d9b959d37706447c1d95",
    "vin_sz":1,
    "tx_index":113417334,
    "ver":1,
    "out":[
        {
            "n":0,
            "value":400000,
            "addr":"15xb5bwoCbSprTNjotfc5VSFSMkUpCQsig",
            "tx_index":113417334,
            "type":0
        },{
            "n":1,
            "value":4310000,
            "addr":"18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp",
            "tx_index":113417334,
            "type":0
        }
    ],
    "size":226
},

That there is one "inputs" array elements with a "prev_out" that was sent to an "addr" of 18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp.  That one array element has a "value" of 4720000. Therefore a previously unspent output received previously at 18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp valued at 4720000 satoshis (0.0472 BTC) are "spent" with this transaction.

Meanwhile there is also a single "out" array element that was sent to an "addr" of 18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp. That one array element has a "value" of 4310000.  Therefore 4310000 satoshis (0.0431 BTC) were "received" at that address with this transaction.

4310000 received less 4720000 spent equals a net change of -410000 (-0.0041 BTC). Therefore this transaction results in a net change of -410000 (-0.0041 BTC) to the value associated with the address 18Zbf9aEKwZTeR92u4tuhQenoen9prSeNp.

jackpf (OP)
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February 23, 2014, 09:43:15 AM
 #6

Wow thanks for the response, I'll give this a go. I tried doing something similar but couldn't get it quite right but hopefully I can now.I opened a ticket on blockchain support but they're not convinced its a bug because nobody else has complained about it, so guess I'll have to do it this way! Thanks!
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