Upgrade Linked List in Blockchain by python

Let's upgrade the linked list to the blockchain. In order to accomplish this, we add a new property to the Block class called the parent's hash.

Take a look at the following code block , If we change the history of BlockA, then the hash value of BlockC will also change; otherwise, it won't. That's the allure of blockchain technology.

import hashlib

import json

class Block:

    id = None

    history = None

    parent_id = None

    parent_hash = None

blockA = Block()

blockA.id = 1

blockA.history = 'He likes Dora'

blockB = Block()

blockB.id = 2

blockB.history = 'She likes Ryder'

blockB.parent_id = blockA.id

blockB.parent_hash = hashlib.sha256(json.dumps(blockA.__dict__).encode('utf-8')).hexdigest()

blockC = Block()

blockC.id = 3

blockC.history = 'She likes Ryder'

blockC.parent_id = blockB.id

blockC.parent_hash = hashlib.sha256(json.dumps(blockB.__dict__).encode('utf-8')).hexdigest()

print("Original parent hash in block C")

print(blockC.parent_hash)

print()

print("No Change in the history on block A:")

print()

blockA.history = 'He likes Dora'

blockB.parent_hash = hashlib.sha256(json.dumps(blockA.__dict__).encode('utf-8')).hexdigest()

blockC.parent_hash = hashlib.sha256(json.dumps(blockB.__dict__).encode('utf-8')).hexdigest()

print()

print("Change History on block A")

print()

blockA.history = 'He doesn\'t likes Ryder'

blockB.parent_hash = hashlib.sha256(json.dumps(blockA.__dict__).encode('utf-8')).hexdigest()

blockC.parent_hash = hashlib.sha256(json.dumps(blockB.__dict__).encode('utf-8')).hexdigest()

print("Ahh! , New parent hash in block C which is different from original one")

print(blockC.parent_hash)

Run the above script 

PS D:\KnowledgeHunt\blockchain\ch1> python .\upgradelinklist.py

Original parent hash in block C

79be004af591f9724f09d47ce0fc9bdb7565f748e56f81447a694a3cfe0393ee

No Change in the history on block A:

79be004af591f9724f09d47ce0fc9bdb7565f748e56f81447a694a3cfe0393ee

Change History on block A

Ahh! , New parent hash in block C which is different from original one

1a11773a77eb6e3555d1936e6b9bc91687fe29336ebe8c41f47114f3fceda9bb