Added source code

Added source code

Author: howCodeORG

README.md

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+Simple Python Blockchain with MINING!
+=====================================
+
+This is the source code for howCode's simple Python Blockchain.
+
+You can watch the video that accompanies this source code here: https://youtu.be/b81Ib_oYbFk

blockchain.py

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+import datetime
+import hashlib
+
+class Block:
+    blockNo = 0
+    data = None
+    next = None
+    hash = None
+    nonce = 0
+    previous_hash = 0x0
+    timestamp = datetime.datetime.now()
+
+    def __init__(self, data):
+        self.data = data
+
+    def hash(self):
+        h = hashlib.sha256()
+        h.update(
+        str(self.nonce).encode('utf-8') +
+        str(self.data).encode('utf-8') +
+        str(self.previous_hash).encode('utf-8') +
+        str(self.timestamp).encode('utf-8') +
+        str(self.blockNo).encode('utf-8')
+        )
+        return h.hexdigest()
+
+    def __str__(self):
+        return "Block Hash: " + str(self.hash()) + "\nBlockNo: " + str(self.blockNo) + "\nBlock Data: " + str(self.data) + "\nHashes: " + str(self.nonce) + "\n--------------"
+
+class Blockchain:
+
+    diff = 20
+    maxNonce = 2**32
+    target = 2 ** (256-diff)
+
+    block = Block("Genesis")
+    dummy = head = block
+
+    def add(self, block):
+
+        block.previous_hash = self.block.hash()
+        block.blockNo = self.block.blockNo + 1
+
+        self.block.next = block
+        self.block = self.block.next
+
+    def mine(self, block):
+        for n in range(self.maxNonce):
+            if int(block.hash(), 16) <= self.target:
+                self.add(block)
+                print(block)
+                break
+            else:
+                block.nonce += 1
+
+blockchain = Blockchain()
+
+for n in range(10):
+    blockchain.mine(Block("Block " + str(n+1)))
+
+while blockchain.head != None:
+    print(blockchain.head)
+    blockchain.head = blockchain.head.next