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Quickstart: Publish & Consume Flow for REST API-style URIs

This quickstart describes a flow to publish Kraken REST API of OCEAN-USD pair price feed, to make it available as free data asset on Ocean, and to consume it.

Here are the steps:

  1. Setup
  2. Alice publishes the API asset
  3. Alice creates a faucet for the asset
  4. Bob gets a free datatoken, then consumes it

Let's go through each step.

1. Setup

Ensure that you've already (a) installed Ocean, and (b) set up locally or remotely.

2. Alice publishes the API asset

In the same Python console:

# Data info
name = "Kraken API OCEAN-USD price feed"
pair = 'OCEANUSD' # Choose the trading pair
interval = '1440' # Choose the time interval in minutes (1440 for daily)

from datetime import datetime, timedelta
end_datetime = datetime.now()
start_datetime = end_datetime - timedelta(days=7) # The previous week
since = int(start_datetime.timestamp() * 1000) # Choose the start time in Unix timestamp
url = f'https://api.kraken.com/0/public/OHLC?pair={pair}&interval={interval}&since={since}'

#create asset
(data_nft, datatoken, ddo) = ocean.assets.create_url_asset(name, url, {"from": alice})
print(f"Just published asset, with did={ddo.did}")

3. Alice creates a faucet for the asset

In the same Python console:

datatoken.create_dispenser({"from": alice})

4. Bob gets a free datatoken, then consumes it

Now, you're Bob. First, download the file.

In the same Python console:

# Set asset did. Practically, you'd get this from Ocean Market. _This_ example uses prior info.
ddo_did = ddo.did

# Bob gets a free datatoken, sends it to the service, and downloads
datatoken.dispense(to_wei(1), {"from": bob})
order_tx_id = ocean.assets.pay_for_access_service(ddo, {"from": bob}).hex()
asset_dir = ocean.assets.download_asset(ddo, bob, './', order_tx_id)

import os
file_name = os.path.join(asset_dir, 'file0')

Now, load the file and use its data.

The data follows the Kraken docs specs for Data, here.

In the same Python console:

# Load from file into memory
with open(file_name, "r") as file:
    # Data is a string with the result inside.
    data_str = file.read().rstrip().replace("'", '"')

import json
data = json.loads(data_str)

# Data is a list of lists
# -Outer dictionary contains 2 keys, one for errors and one for the result with the pair.
# -Inner dictionary have 9 entries each: Kline open time, Open price, High price, Low price, close Price, Vol, ..
# Get close price
close_prices = [float(data_at_day[4]) for data_at_day in data['result'][pair]]
print(f"close prices: {close_prices}")