Blockchain Exchange Python API

Table of Contents

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Last Update: 2020-05-17

• Features
• Installation
  • For general use
  • For development
• Prerequisites for trading
• Demos
  • Listen to all public channels
  • Create market and limit orders
• TODO

Features

• Subscribe to all websocket channels available at blockchain.com | exchage:

  • Heartbeat
  • Orderbook L2
  • Orderbook L3
  • Prices
  • Symbols
  • Ticker
  • Trades
  • Trading
  • Balance

• Subscription to new channels doesn’t require client restart

• Create Market orders
• Create Limit orders

All API is available through a websocket client:

import logging
from bcx.client import BlockchainWebsocketClient
logging.basicConfig(level=logging.INFO)
client = BlockchainWebsocketClient()

See our documentation for API reference and gallery of examples for more info.

Installation

In order to get started you should have Python>=3.6 installed.

For general use

This is as simple as running

pip install bcx

For development

• Get source code

  git clone git@github.com:ilya-bc/blockchain-exchange-api.git
  cd blockchain-exchange-api

• Install package in editable mode. Since there are hundred ways to do that, a standardised way for this project is with Makefile. It will create virtual environment with pipenv based on python==3.7 and install all necessary dependencies for development

  make install-dev

• If you don’t have pipenv or prefer to manage a virtual environment using different tools, then you can use

  pip install -e '.[dev]'

• In order to build documentation

  (cd docs && make html)
  open docs/build/html/index.html

  Important: Building documentation will execute example scripts, so be extremely cautious when writing sample scripts that make use of trading channel.

Prerequisites for trading

Actual trading and accessing balance of your account requires authentication with an API key. In order to get one:

1. You should have an account at blockchain.com | exchange

2. Create API key here and store information. Note, you can have setup key with permissions view and view & trade.

3. You should receive an email asking you to activate API key.

4. Setup the following environment variable

   export BLOCKCHAIN_API_SECRET="__ENTER_YOUR_API_SECRET_HERE__"

   Tip: If you use pipenv then you can just put it into .env file (ignored by git) at the root of the cloned directory

Demos

Listen to all public channels

• Script
• Script extended

Note: There are time.sleep(2) between calling different methods, in order to be able to see intermediate results.

Create market and limit orders

• Script
• Script extened

Note: Both orders got rejected (expected behaviour) because of invalid quantity and price being to big.

TODO

• Tests
• Something weird is going on with unsubscribing from channels in bulk for the following ones:

  [
  {"channel": "l2", "symbol": "BTC-USD"},
  {"channel": "ticker", "symbol": "BTC-USD"},
  {"channel": "trades", "symbol": "BTC-USD"}
  ]

• Check contradiction with API docs on prices channel

  [
  {"seqnum":1,"event":"subscribed","channel":"prices","symbol":"BTC-USD","granularity":60},
  {"seqnum":2,"event":"subscribed","channel":"prices","symbol":"ETH-USD","granularity":60},
  {"seqnum":3,"event":"subscribed","channel":"prices","symbol":"BTC-USD","granularity":300},
  {"seqnum":4,"event":"subscribed","channel":"prices","symbol":"ETH-USD","granularity":300}
  ]

• Docs doesn’t say that ticker channel sends update events

  [
  {"seqnum":0,"event":"subscribed","channel":"ticker","symbol":"BTC-USD"},
  {"seqnum":1,"event":"snapshot","channel":"ticker","symbol":"BTC-USD","price_24h":8744.9,"volume_24h":155.77132628,"last_trade_price":8881.0},
  {"seqnum":2,"event":"updated","channel":"ticker","symbol":"BTC-USD","price_24h":8754.8,"volume_24h":155.70446581}
  ]