Add BlockChain concept (prateekiiest#160)

Author: jadia

Code-Sleep-Python/primitiveBlockChain/Blockchain-Structure.png

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+# Primitive BlockChain Implementation
+
+![Blockchain-Structure.png](Blockchain-Structure.png)

Code-Sleep-Python/primitiveBlockChain/README.md

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+#!/bin/python3
+# Primitive implementaion of BlockChain Concept
+
+import hashlib as hasher
+import datetime as date
+
+# Block structure
+
+
+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.hashBlock()
+
+# Create hash of block
+    def hashBlock(self):
+        sha = hasher.sha256()
+        sha.update((str(self.index) +
+                    str(self.timestamp) +
+                    str(self.data) +
+                    str(self.previous_hash)).encode())
+        return sha.hexdigest()
+
+
+# Create genesis block
+
+def createGenesisBlock():
+    return Block(0, date.datetime.now(), "Genesis Block", "0")
+
+# Create chain of blocks
+
+
+def nextBlock(lastBlock):
+    id = lastBlock.index + 1
+    timeStp = date.datetime.now()
+    data = "Block number: " + str(id)
+    hash256 = lastBlock.hash
+    return Block(id, timeStp, data, hash256)
+
+
+# Create blockchain and add genesis block
+
+blockchain = [createGenesisBlock()]
+previousBlock = blockchain[0]
+
+
+# How many blocks to add after genesis block
+noOfBlocks = 20
+
+# Add blocks to chain
+for i in range(0, noOfBlocks):
+    #    print(f"i value: {i}")
+    addBlock = nextBlock(previousBlock)
+    blockchain.append(addBlock)
+    previousBlock = addBlock
+    # Broadcast
+    print(f"Block #{addBlock.index} has been added to blockchain!")
+    print(f"Hash: {addBlock.hash} \n")