This notebook is based on this blog post
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import hashlib as hasher
import datetime as date
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class Block:
def __init__(self, index, timestamp, data, previous_hash):
self.index = index
self.timestamp = timestamp
self.data = data
self.previous_hash = previous_hash
self.hash = self.hash_block()
def hash_block(self):
sha = hasher.sha256()
sha.update(str(self.index).encode('utf8') +
str(self.timestamp).encode('utf8') +
str(self.data).encode('utf8') +
str(self.previous_hash).encode('utf8'))
return sha.hexdigest()
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def create_genesis_block():
'''
Manually construct a block with
index zero and arbitrary previous hash
'''
return Block(0, date.datetime.now(), "Genesis Block", "0")
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def next_block(last_block):
this_index = last_block.index + 1
this_timestamp = date.datetime.now()
this_data = "Hey! I'm block " + str(this_index)
this_hash = last_block.hash
return Block(this_index, this_timestamp, this_data, this_hash)
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# Create the blockchain and add the genesis block
blockchain = [create_genesis_block()]
previous_block = blockchain[0]
# How many blocks should we add to the chain
# after the genesis block
num_of_blocks_to_add = 20
# Add blocks to the chain
for i in range(0, num_of_blocks_to_add):
block_to_add = next_block(previous_block)
blockchain.append(block_to_add)
previous_block = block_to_add
# Tell everyone about it!
print ("Block #{} has been added to the blockchain!".format(block_to_add.index))
print ("Hash: {}\n".format(block_to_add.hash) )
Implement the rest of the system as on or more Python modules. The code is explained here.
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