Replaced Binance API with Kraken example (#1382)

READMEs/publish-flow-restapi.md

@@ -5,7 +5,7 @@ SPDX-License-Identifier: Apache-2.0
 
 # Quickstart: Publish & Consume Flow for REST API-style URIs
 
-This quickstart describes a flow to publish Binance REST API of ETH price feed, to make it available as free data asset on Ocean, and to consume it.
+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:
 
@@ -24,13 +24,16 @@ Ensure that you've already (a) [installed Ocean](install.md), and (b) [set up lo
 
 In the same Python console:
 ```python
-#data info
-name = "Binance API v3 klines"
+# 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
-url = f"https://api.binance.com/api/v3/klines?symbol=ETHUSDT&interval=1d&startTime={int(start_datetime.timestamp())*1000}&endTime={int(end_datetime.timestamp())*1000}"
+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})
@@ -64,24 +67,24 @@ file_name = os.path.join(asset_dir, 'file0')
 
 Now, load the file and use its data.
 
-The data follows the Binance docs specs for Kline/Candlestick Data, [here](https://binance-docs.github.io/apidocs/spot/en/#kline-candlestick-data).
+The data follows the Kraken docs specs for Data, [here](https://docs.kraken.com/rest/#tag/Market-Data/operation/getOHLCData).
 
 In the same Python console:
 ```python
 
-#load from file into memory
+# Load from file into memory
 with open(file_name, "r") as file:
-    #data_str is a string holding a list of lists '[[1663113600000,"1574.40000000", ..]]'
-    data_str = file.read().rstrip().replace('"', '')
-
-
-data = eval(data_str)
-
-#data is a list of lists
-# -Outer list has one 7 entries; one entry per day.
-# -Inner lists have 12 entries each: Kline open time, Open price, High price, Low price, close Price, Vol, ..
-
-#get close prices
-close_prices = [float(data_at_day[4]) for data_at_day in data]
+    # 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}")
 ```