Update pow_algorithm.py with return type

blockchain/pow_algorithm.py

@@ -2,18 +2,34 @@
 # Title: Proof of Work Algorithm for Blockchain
 
 ## Algorithm Statement:
-The algorithm implements the Proof of Work (PoW) consensus mechanism used in
+The algorithm implements the Proof of Work (PoW) consensus mechanism used in 
-blockchain to validate blocks. PoW ensures participants (miners) perform a
+blockchain to validate blocks. PoW ensures participants (miners) perform a 
-computational task to create a valid block and add it to the blockchain. The
+computational task to create a valid block and add it to the blockchain. The 
 difficulty is defined by the number of leading zeros required in the block hash.
 """
 
 import hashlib
 import time
 
-
 class Block:
-    def __init__(self, index, previous_hash, transactions, timestamp, difficulty):
+    def __init__(
+        self, 
+        index: int, 
+        previous_hash: str, 
+        transactions: str, 
+        timestamp: float, 
+        difficulty: int
+    ) -> None:
+        """
+        Initializes a Block object with the specified parameters.
+
+        Parameters:
+        - index (int): The index of the block in the blockchain.
+        - previous_hash (str): The hash of the previous block.
+        - transactions (str): The list of transactions in the block.
+        - timestamp (float): The time when the block was created (in Unix timestamp format).
+        - difficulty (int): The difficulty level for mining this block.
+        """
         self.index = index
         self.previous_hash = previous_hash
         self.transactions = transactions
@@ -22,11 +38,14 @@ class Block:
         self.difficulty = difficulty
         self.hash = self.compute_hash()
 
-    def compute_hash(self):
+    def compute_hash(self) -> str:
         """
         Generates the hash of the block content.
         Combines index, previous hash, transactions, timestamp, and nonce into a string,
         which is then hashed using SHA-256.
+        
+        Returns:
+        - str: The hash of the block.
         """
         block_string = (
             f"{self.index}{self.previous_hash}{self.transactions}{self.timestamp}"
@@ -34,55 +53,72 @@ class Block:
         )
         return hashlib.sha256(block_string.encode()).hexdigest()
 
-    def mine_block(self):
+    def mine_block(self) -> None:
         """
         Performs Proof of Work by adjusting the nonce until a valid hash is found.
-        A valid hash has the required number of leading zeros based on the difficulty
+        A valid hash has the required number of leading zeros based on the difficulty level.
-        level.
+        
+        Returns:
+        - None
         """
-        target = (
+        target = '0' * self.difficulty  # Target hash should start with 'difficulty' zeros
-            "0" * self.difficulty
+        while self.hash[:self.difficulty] != target:
-        )  # Target hash should start with 'difficulty' zeros
-        while self.hash[: self.difficulty] != target:
             self.nonce += 1
             self.hash = self.compute_hash()
 
         print(f"Block mined with nonce {self.nonce}, hash: {self.hash}")
 
-
 class Blockchain:
-    def __init__(self, difficulty):
+    def __init__(self, difficulty: int) -> None:
+        """
+        Initializes the blockchain with a given difficulty level.
+
+        Parameters:
+        - difficulty (int): The difficulty level for mining blocks in this blockchain.
+        
+        Returns:
+        - None
+        """
         self.chain = []
         self.difficulty = difficulty
         self.create_genesis_block()
 
-    def create_genesis_block(self):
+    def create_genesis_block(self) -> None:
         """
         Creates the first block in the blockchain (the Genesis block).
+        
+        Returns:
+        - None
         """
         genesis_block = Block(0, "0", "Genesis Block", time.time(), self.difficulty)
         genesis_block.mine_block()
         self.chain.append(genesis_block)
 
-    def add_block(self, transactions):
+    def add_block(self, transactions: str) -> None:
         """
         Adds a new block to the blockchain after performing Proof of Work.
+
+        Parameters:
+        - transactions (str): The list of transactions to be added in the new block.
+        
+        Returns:
+        - None
         """
         previous_block = self.chain[-1]
         new_block = Block(
-            len(self.chain),
+            len(self.chain), previous_block.hash, transactions, time.time(), 
-            previous_block.hash,
+            self.difficulty
-            transactions,
-            time.time(),
-            self.difficulty,
         )
         new_block.mine_block()
         self.chain.append(new_block)
 
-    def is_chain_valid(self):
+    def is_chain_valid(self) -> bool:
         """
-        Verifies the integrity of the blockchain by ensuring each block's previous
+        Verifies the integrity of the blockchain by ensuring each block's previous 
         hash matches and that all blocks meet the Proof of Work requirement.
+
+        Returns:
+        - bool: True if the blockchain is valid, False otherwise.
         """
         for i in range(1, len(self.chain)):
             current_block = self.chain[i]
@@ -98,13 +134,14 @@ class Blockchain:
 
         return True
 
-
 # Test cases
 
-
+def test_blockchain() -> None:
-def test_blockchain():
     """
     Test cases for the Blockchain proof of work algorithm.
+    
+    Returns:
+    - None
     """
     # Create blockchain with difficulty level of 4 (hash should start with 4 zeros)
     blockchain = Blockchain(difficulty=4)
@@ -117,23 +154,10 @@ def test_blockchain():
     assert blockchain.is_chain_valid(), "Blockchain should be valid"
 
     # Tamper with the blockchain and check validation
-    blockchain.chain[
+    blockchain.chain[1].transactions = "Transaction 1: Alice pays Bob 50 BTC"  # Tampering
-        1
+    assert not blockchain.is_chain_valid(), "Blockchain should be invalid due to tampering"
-    ].transactions = "Transaction 1: Alice pays Bob 50 BTC"  # Tampering
-    assert (
-        not blockchain.is_chain_valid()
-    ), "Blockchain should be invalid due to tampering"
 
     print("All test cases passed.")
 
-
 if __name__ == "__main__":
     test_blockchain()
-
-"""
-# Output:
-- Block mined with nonce X, hash: 0000abcd...
-- Block mined with nonce Y, hash: 0000xyz...
-- Block mined with nonce Z, hash: 0000pqrs...
-- All test cases passed.
-"""