Part 2 Blockchain Programming Using Python.pdf
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Simple Blockchain working using Python
![#Part 1: Building a Blockchain
class Blockchain:
def __init__(self):
self.chain = [ ]
self.create_block(proof = 1, previous_hash = '0')
def create_block(self, proof, previous_hash):
block = {'index': len(self.chain) + 1,
'timestamp': str(datetime.datetime.now()),
'proof': proof,
'previous_hash': previous_hash}
self.chain.append(block)
return block
4](https://image.slidesharecdn.com/part2blockchainprogrammingusingpython-250625072122-049fddf9/85/Part-2-Blockchain-Programming-Using-Python-pdf-4-320.jpg)
![8 def is_chain_valid(self, chain):
previous_block = chain[0]
block_index = 1
while block_index < len(chain):
block = chain[block_index]
if block['previous_hash'] != self.hash(previous_block):
return False
previous_proof = previous_block['proof']
proof = block['proof']
hash_operation = hashlib.sha256(str(proof**2 previous_proof**2).encode()).hexdigest()
if hash_operation[:4] != '0000':
return False
previous_block = block
block_index += 1
return True](https://image.slidesharecdn.com/part2blockchainprogrammingusingpython-250625072122-049fddf9/85/Part-2-Blockchain-Programming-Using-Python-pdf-8-320.jpg)
![9
# Part 2 - Mining our Blockchain
# Creating a Web App
app = Flask(__name__)
app.config['JSONIFY_PRETTYPRINT_REGULAR'] = False
# Creating a Blockchain
blockchain = Blockchain()
from flask import Flask
app = Flask(__name__)
@app.route ('/’)
def hello_world():
return 'Hello, World!'
A minimal Flask application looks something like this:](https://image.slidesharecdn.com/part2blockchainprogrammingusingpython-250625072122-049fddf9/85/Part-2-Blockchain-Programming-Using-Python-pdf-9-320.jpg)
![10
# Mining a new block
@app.route('/mine_block', methods = ['GET'])
def mine_block():
previous_block = blockchain.get_previous_block()
previous_proof = previous_block['proof']
proof = blockchain.proof_of_work(previous_proof)
previous_hash = blockchain.hash(previous_block)
block = blockchain.create_block(proof, previous_hash)
response = {'message': 'Congratulations, you just mined a block!',
'index': block['index'],
'timestamp': block['timestamp'],
'proof': block['proof'],
'previous_hash': block['previous_hash']}
return jsonify(response), 200 # HTTP code 200 is for success , OK](https://image.slidesharecdn.com/part2blockchainprogrammingusingpython-250625072122-049fddf9/85/Part-2-Blockchain-Programming-Using-Python-pdf-10-320.jpg)
![11
# Getting the full Blockchain
@app.route('/get_chain', methods = ['GET'])
def get_chain():
response = {'chain': blockchain.chain,
'length': len(blockchain.chain)}
return jsonify(response), 200
# Checking if the Blockchain is valid
@app.route('/is_valid', methods = ['GET'])
def is_valid():
is_valid = blockchain.is_chain_valid(blockchain.chain)
if is_valid:
response = {'message': 'All good. The Blockchain is valid.'}
else:
response = {'message’: ‘The Blockchain is not valid.'}
return jsonify(response), 200](https://image.slidesharecdn.com/part2blockchainprogrammingusingpython-250625072122-049fddf9/85/Part-2-Blockchain-Programming-Using-Python-pdf-11-320.jpg)
Part 2 Blockchain Programming Using Python.pdf
- 3. Importing the Libraries import datetime import hashlib import json from flask import Flask, jsonify 3
- 4. #Part 1: Building a Blockchain class Blockchain: def __init__(self): self.chain = [ ] self.create_block(proof = 1, previous_hash = '0') def create_block(self, proof, previous_hash): block = {'index': len(self.chain) + 1, 'timestamp': str(datetime.datetime.now()), 'proof': proof, 'previous_hash': previous_hash} self.chain.append(block) return block 4
- 5. #Part 1: Building a Blockchain def create_block(self, proof, previous_hash): block = {'index': len(self.chain) + 1, 'timestamp': str(datetime.datetime.now()), 'proof': proof, 'previous_hash': previous_hash} self.chain.append(block) return block 5
- 7. Introduction 7 def hash(self, block): encoded_block = json.dumps(block, sort_keys = True).encode() return hashlib.sha256(encoded_block).hexdigest()
- 8. 8 def is_chain_valid(self, chain): previous_block = chain[0] block_index = 1 while block_index < len(chain): block = chain[block_index] if block['previous_hash'] != self.hash(previous_block): return False previous_proof = previous_block['proof'] proof = block['proof'] hash_operation = hashlib.sha256(str(proof**2 previous_proof**2).encode()).hexdigest() if hash_operation[:4] != '0000': return False previous_block = block block_index += 1 return True
- 9. 9 # Part 2 - Mining our Blockchain # Creating a Web App app = Flask(__name__) app.config['JSONIFY_PRETTYPRINT_REGULAR'] = False # Creating a Blockchain blockchain = Blockchain() from flask import Flask app = Flask(__name__) @app.route ('/’) def hello_world(): return 'Hello, World!' A minimal Flask application looks something like this:
- 10. 10 # Mining a new block @app.route('/mine_block', methods = ['GET']) def mine_block(): previous_block = blockchain.get_previous_block() previous_proof = previous_block['proof'] proof = blockchain.proof_of_work(previous_proof) previous_hash = blockchain.hash(previous_block) block = blockchain.create_block(proof, previous_hash) response = {'message': 'Congratulations, you just mined a block!', 'index': block['index'], 'timestamp': block['timestamp'], 'proof': block['proof'], 'previous_hash': block['previous_hash']} return jsonify(response), 200 # HTTP code 200 is for success , OK
- 11. 11 # Getting the full Blockchain @app.route('/get_chain', methods = ['GET']) def get_chain(): response = {'chain': blockchain.chain, 'length': len(blockchain.chain)} return jsonify(response), 200 # Checking if the Blockchain is valid @app.route('/is_valid', methods = ['GET']) def is_valid(): is_valid = blockchain.is_chain_valid(blockchain.chain) if is_valid: response = {'message': 'All good. The Blockchain is valid.'} else: response = {'message’: ‘The Blockchain is not valid.'} return jsonify(response), 200
- 12. 12 # Running the app app.run(host = ‘0.0.0.0’, port = 5000)