dirkandre / blockchain-in-python

Built-up a functional Blockchain with Python code

Blockchain-in-Python

Built-up a functional Blockchain with Python code

Main Blockchain functunality built-up inside Python documentation as good as known ... done by #Dirk Wollschlaeger

use two classes "Block" and "Blockchain" Variables following variables used inside the use-case:

1. prev_hash = each block has as result as PoW one hash result, used for next block calculation
2. nonce = used digit counter until hash function fulfilled requested difficulty
3. data = data content inside the requested new block (could be all value as string)
4. current_hash = new calculated hash
5. difficulty = the requested number of "0" at the beginning of the hash result
6. found = used as boaland, fulfilled calculated hash the difficulty (yes/no)
7. block = as array and storages for each block 1,2,3,4, ...
8. chain = storred Blockchain
9. genesis = start of the blockchain to get the first block initiated Classes: i) Block = all about to get a new block mind ii)Blockchain = put the Blockchain alive and usable as database Function def: a) init = initialisation
   b) repr = help function for during setup the blockchain to check how the hases Block 0 and Block 1 look like, used space {} brackets to built-up a dynamic return c) block_string = put the data together wish as to be used for hash calc d) hash1 = used lib function hashlib and calculation out of block_string the right SHA256 hash e) mine = mining process, used difficulty f) add = add put the new block to the array g) last_block = is check, are there a first block, if yes h) build_block = initiate class Block to build a new block import hashlib to use Hash function SHA256

import hashlib, datetime

class Block: prev_hash = None nonce = -1 data = None timestamp = None

current_hash = None

def __init__ (self, prev_hash, data, timestamp):
    self.prev_hash = prev_hash
    self.data = data
    self.timestamp = timestamp

def __repr__ (self):
    return "Block {0} (prev. {1})".format (
    self.current_hash,
    self.prev_hash
    )

@property
def block_string(self):
    return "{0}-{1}-{2}-{3}".format(
    self.prev_hash,
    self.data,
    self.timestamp,
    self.nonce
    )

def hash1 (self):
    return hashlib.sha256(bytes(self.block_string, "utf-8")).hexdigest()

def mine (self, difficulty):
    found = False
    while not found:
        self.nonce +=1
        self.current_hash = self.hash1()
        if self.current_hash[0:difficulty]== "0" * difficulty:
            found = True

class Blockchain: blocks = [] timestamp_counter = [] difficulty = 5

def add(self, block):
    block.mine(self.difficulty)
    self.blocks.append(block)
    

@property
def last_block(self):
    return self.blocks[-1] if len(self.blocks) else None 

def build_block(self, data, timestamp):
    if self.last_block:
        block = Block(self.last_block.current_hash, data, timestamp)
        self.add(block)
    else:
        raise Exception ("Missing first Block")

chain = Blockchain() i = 0 timestamp = str(datetime.datetime.now()) timestamp_counter = f"Block:{i} " + timestamp genesis = Block(None, "GENESIS", timestamp) chain.add(genesis)

amount_blocks = input("How much Blocks you want to add ? = " "")

while i < int(amount_blocks):

chain.build_block(input(f"What are the Block data you want to add for the {i+1} Block? = " ""), timestamp=datetime.datetime.now())
timestamp = str(datetime.datetime.now())
timestamp_counter = timestamp_counter + f", Block:{i+1} " + timestamp
i  += 1

for b in chain.blocks: print(b)

print("Last block nonce is ", chain.last_block.nonce) print("timestamps for all blocks are ", timestamp_counter)