[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

blockchain/pow_algorithm.py

@@ -11,6 +11,7 @@ difficulty is defined by the number of leading zeros required in the block hash.
 import hashlib
 import time
 
+
 class Block:
     def __init__(
         self,
@@ -18,7 +19,7 @@ class Block:
         previous_hash: str,
         transactions: str,
         timestamp: float,
-        difficulty: int
+        difficulty: int,
     ) -> None:
         """
         Initializes a Block object with the specified parameters.
@@ -61,13 +62,16 @@ class Block:
         Returns:
         - None
         """
-        target = '0' * self.difficulty  # Target hash should start with 'difficulty' zeros
-        while self.hash[:self.difficulty] != target:
+        target = (
+            "0" * self.difficulty
+        )  # 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: int) -> None:
         """
@@ -106,8 +110,11 @@ class Blockchain:
         """
         previous_block = self.chain[-1]
         new_block = Block(
-            len(self.chain), previous_block.hash, transactions, time.time(), 
-            self.difficulty
+            len(self.chain),
+            previous_block.hash,
+            transactions,
+            time.time(),
+            self.difficulty,
         )
         new_block.mine_block()
         self.chain.append(new_block)
@@ -134,8 +141,10 @@ class Blockchain:
 
         return True
 
+
 # Test cases
 
+
 def test_blockchain() -> None:
     """
     Test cases for the Blockchain proof of work algorithm.
@@ -154,10 +163,15 @@ def test_blockchain() -> None:
     assert blockchain.is_chain_valid(), "Blockchain should be valid"
 
     # Tamper with the blockchain and check validation
-    blockchain.chain[1].transactions = "Transaction 1: Alice pays Bob 50 BTC"  # Tampering
-    assert not blockchain.is_chain_valid(), "Blockchain should be invalid due to tampering"
+    blockchain.chain[
+        1
+    ].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()