Create app.py

app.py

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+import streamlit as st
+import hashlib
+import time
+import json
+
+# Blockchain Classes
+class Block:
+    def __init__(self, index, timestamp, transactions, previous_hash):
+        self.index = index
+        self.timestamp = timestamp
+        self.transactions = transactions
+        self.previous_hash = previous_hash
+        self.hash = self.calculate_hash()
+
+    def calculate_hash(self):
+        block_content = json.dumps({
+            "index": self.index,
+            "timestamp": self.timestamp,
+            "transactions": self.transactions,
+            "previous_hash": self.previous_hash
+        }, sort_keys=True).encode()
+        return hashlib.sha256(block_content).hexdigest()
+
+class Blockchain:
+    def __init__(self):
+        self.chain = [self.create_genesis_block()]
+        self.pending_transactions = []
+
+    def create_genesis_block(self):
+        return Block(0, time.time(), [], "0")
+
+    def get_latest_block(self):
+        return self.chain[-1]
+
+    def add_transaction(self, transaction):
+        self.pending_transactions.append(transaction)
+
+    def mine_block(self):
+        if not self.pending_transactions:
+            return None
+        
+        new_block = Block(
+            index=len(self.chain),
+            timestamp=time.time(),
+            transactions=self.pending_transactions,
+            previous_hash=self.get_latest_block().hash
+        )
+        self.chain.append(new_block)
+        self.pending_transactions = []  # Clear pending transactions
+        return new_block
+
+    def is_chain_valid(self):
+        for i in range(1, len(self.chain)):
+            current_block = self.chain[i]
+            previous_block = self.chain[i - 1]
+            
+            if current_block.hash != current_block.calculate_hash():
+                return False
+            
+            if current_block.previous_hash != previous_block.hash:
+                return False
+        
+        return True
+
+# Streamlit App
+st.title("Simple Blockchain Demo")
+st.sidebar.header("Add a Transaction")
+
+# Initialize Blockchain
+if "blockchain" not in st.session_state:
+    st.session_state.blockchain = Blockchain()
+
+blockchain = st.session_state.blockchain
+
+# Add a Transaction
+sender = st.sidebar.text_input("Sender")
+recipient = st.sidebar.text_input("Recipient")
+amount = st.sidebar.number_input("Amount", min_value=0.01, step=0.01)
+
+if st.sidebar.button("Add Transaction"):
+    if sender and recipient and amount:
+        blockchain.add_transaction({"from": sender, "to": recipient, "amount": amount})
+        st.sidebar.success("Transaction added to the pool!")
+    else:
+        st.sidebar.error("Please provide valid transaction details.")
+
+# Mine a Block
+if st.button("Mine a Block"):
+    new_block = blockchain.mine_block()
+    if new_block:
+        st.success(f"Block {new_block.index} mined successfully!")
+    else:
+        st.error("No transactions to mine.")
+
+# Display Blockchain
+st.subheader("Blockchain Ledger")
+for block in blockchain.chain:
+    st.write({
+        "Index": block.index,
+        "Timestamp": time.ctime(block.timestamp),
+        "Transactions": block.transactions,
+        "Previous Hash": block.previous_hash,
+        "Hash": block.hash,
+    })
+
+# Validate Blockchain
+if st.button("Validate Blockchain"):
+    if blockchain.is_chain_valid():
+        st.success("Blockchain is valid!")
+    else:
+        st.error("Blockchain is invalid!")