Update blockchain_algorithm.py

Blockchain/blockchain_algorithm.py

@@ -2,35 +2,52 @@
 import time
 
 class block:
-	def __init__ (self, timestamp, data, previousHash = ' '):
-		self.timestamp = timestamp
-		self.data = data
-		self.previousHash = previousHash
-		self.hash = self.calculateHash()
+        def __init__ (self, timestamp, data, previousHash = ' '):
+                self.timestamp = timestamp
+                self.data = data
+                self.previousHash = previousHash
+                self.hash = self.calculateHash()
 
-	def calculateHash(self):
-		return sha256((str(self.timestamp) + str(self.data) + str(self.previousHash)).encode()).hexdigest()
+        def calculateHash(self):
+                return sha256((str(self.timestamp) + str(self.data) + str(self.previousHash)).encode()).hexdigest()
 
 
 class blockchain:
-	def __init__(self):
-		self.chain = [self.createGenesis()]
+        def __init__(self):
+                self.chain = [self.createGenesis()]
 
-	def createGenesis(self):
-		return block(time.ctime(), "genesisBlock", "00000")
+        def createGenesis(self):
+                return block(time.ctime(), "genesisBlock", "00000")
 
-	def mineBlock(self, data):
-		node = block(time.ctime(), data, self.chain[-1].hash)
-		# mining a new block to the blockchain
-		self.chain.append(node)
+        def mineBlock(self, data):
+                if not self.checkChain():
+                    return "Mining unsuccessfully"
+                node = block(time.ctime(), data, self.chain[-1].hash)
+                # mining a new block to the blockchain
+                self.chain.append(node)
+                return "New Block mined successfully"
+
 
-	def printBlockchain(self):
-		for i in range(len(self.chain)):
-			print("\n-----Block ", i ,"---------\n timestamp = "\
-				       , self.chain[i].timestamp,"\n data = ", \
-				       		self.chain[i].data, "\n previousHash = ",\
-				       		 self.chain[i].previousHash,"\n hash = ", \
-				       		    self.chain[i].hash)
+        def checkChain(self):
+            for i in range(len(self.chain)):
+                if i > 0 and self.chain[i-1].hash != self.chain[i].previousHash:
+                    return False
+
+            return True
+
+        def printBlockchain(self):
+                if self.checkChain():
+                        print("Chain is valid")
+                else:
+                    print("Chain is invalid")
+                    return 0
+
+                for i in range(len(self.chain)):    
+                    print("\n-----Block ", i ,"---------\n timestamp = "\
+                                       , self.chain[i].timestamp,"\n data = ", \
+                                                self.chain[i].data, "\n previousHash = ",\
+                                                 self.chain[i].previousHash,"\n hash = ", \
+                                                    self.chain[i].hash)
 
 
 
@@ -40,8 +57,8 @@ def printBlockchain(self):
 
 # sending data to get mined 
 print("\n\n ----> Mining New Block -->")
-CEVcoin.mineBlock(data)
 
-print("\n\n ----> New Block mined successfully --> ")
+
+print("\n\n ----> ",CEVcoin.mineBlock(data)," --> ")
 
 CEVcoin.printBlockchain()