snakecoin.py

import hashlib as hasher
import datetime as date

# Define what a Snakecoin block is
class Block:
  def __init__(self, index, timestamp, data, previous_hash):
    self.index = index
    self.timestamp = timestamp
    self.data = data
    self.previous_hash = previous_hash
    self.hash = self.hash_block()
  
  def hash_block(self):
    sha = hasher.sha256()
    sha.update(str(self.index) + str(self.timestamp) + str(self.data) + str(self.previous_hash))
    return sha.hexdigest()

# Generate genesis block
def create_genesis_block():
  # Manually construct a block with
  # index zero and arbitrary previous hash
  return Block(0, date.datetime.now(), "Genesis Block", "0")

# Generate all later blocks in the blockchain
def next_block(last_block):
  this_index = last_block.index + 1
  this_timestamp = date.datetime.now()
  this_data = "Hey! I'm block " + str(this_index)
  this_hash = last_block.hash
  return Block(this_index, this_timestamp, this_data, this_hash)

# Create the blockchain and add the genesis block
blockchain = [create_genesis_block()]
previous_block = blockchain[0]

# How many blocks should we add to the chain
# after the genesis block
num_of_blocks_to_add = 20

# Add blocks to the chain
for i in range(0, num_of_blocks_to_add):
  block_to_add = next_block(previous_block)
  blockchain.append(block_to_add)
  previous_block = block_to_add
  # Tell everyone about it!
  print "Block #{} has been added to the blockchain!".format(block_to_add.index)
  print "Hash: {}\n".format(block_to_add.hash) 

sha.update(str(self.index).encode('utf-8') + str(self.timestamp).encode('utf-8') + str(self.data).encode('utf-8') + str(self.previous_hash).encode('utf-8'))

You're right !

worked python3 version:

import hashlib
import time


class Block:
    def __init__(self, index: int, timestamp: int, data: str, previous_hash):
        """
        :param index: block index
        :param timestamp: millisecond
        :param data: block real data
        :param previous_hash: previous block hash
        """
        self.index = index
        self.timestamp = timestamp
        self.data = data
        self.previous_hash = previous_hash
        self.hash = self.hash_block()

    def hash_block(self):
        sha = hashlib.sha256()
        seq = [
            str(x) for x in [self.index, self.timestamp, self.data, self.previous_hash]
        ]
        sha.update("".join(seq).encode("utf8"))
        return sha.hexdigest()

    def __str__(self):
        return f"Block:index={self.index}&timestamp={self.timestamp}&data={self.data}&hash={self.hash}"


def get_cur_millisecond():
    return int(round(time.time() * 1000))


def create_genesis_block():
    return Block(0, get_cur_millisecond(), "snake coin genesis block", "0")


def next_block(previous_block: Block):
    index = previous_block.index + 1
    return Block(
        index=index,
        timestamp=get_cur_millisecond(),
        data=f"this is block #{index}",
        previous_hash=previous_block.hash,
    )


def make_test_block_chain():
    block_chain = [create_genesis_block()]
    previous_block = block_chain[0]
    for _ in range(20):
        block = next_block(previous_block)
        block_chain.append(block)
        previous_block = block
        # broadcast: tell everyone about it!
        print(f"Block #{block.index} has been added to the blockchain! detail: {block}")
        time.sleep(1)


if __name__ == "__main__":
    make_test_block_chain()

worked python3 version:

import hashlib
import time


class Block:
    def __init__(self, index: int, timestamp: int, data: str, previous_hash):
        """
        :param index: block index
        :param timestamp: millisecond
        :param data: block real data
        :param previous_hash: previous block hash
        """
        self.index = index
        self.timestamp = timestamp
        self.data = data
        self.previous_hash = previous_hash
        self.hash = self.hash_block()

    def hash_block(self):
        sha = hashlib.sha256()
        seq = [
            str(x) for x in [self.index, self.timestamp, self.data, self.previous_hash]
        ]
        sha.update("".join(seq).encode("utf8"))
        return sha.hexdigest()

    def __str__(self):
        return f"Block:index={self.index}&timestamp={self.timestamp}&data={self.data}&hash={self.hash}"


def get_cur_millisecond():
    return int(round(time.time() * 1000))


def create_genesis_block():
    return Block(0, get_cur_millisecond(), "snake coin genesis block", "0")


def next_block(previous_block: Block):
    index = previous_block.index + 1
    return Block(
        index=index,
        timestamp=get_cur_millisecond(),
        data=f"this is block #{index}",
        previous_hash=previous_block.hash,
    )


def make_test_block_chain():
    block_chain = [create_genesis_block()]
    previous_block = block_chain[0]
    for _ in range(20):
        block = next_block(previous_block)
        block_chain.append(block)
        previous_block = block
        # broadcast: tell everyone about it!
        print(f"Block #{block.index} has been added to the blockchain! detail: {block}")
        time.sleep(1)


if __name__ == "__main__":
    make_test_block_chain()

Tested this out and it worked great! Thanks!

import hashlib as hasher
import datetime as date

class Block:
    def __init__(self, index, timestamp, data, previous_hash):
        self.index = index
        self.timestamp = timestamp
        self.data = data
        self.previous_hash = previous_hash
        self.hash = self.hash_block()

    def hash_block(self):
        sha = hasher.sha256()
        sha.update((str(self.index) + str(self.timestamp) + str(self.data) + str(self.previous_hash)).encode())   #changed line
        return sha.hexdigest()

def create_genesis_block():
    return Block(0, date.datetime.now(), "Genesis Block", 0)

def next_block(last_block):
    this_index = last_block.index + 1
    this_timestamp = date.datetime.now()
    this_data = "Hey! I'm block " + str(this_index)
    this_hash = last_block.hash
    return Block(this_index, this_timestamp, this_data, this_hash)

blockchain = [create_genesis_block()]
previous_block = blockchain[0]

num_of_blocks_to_add = 20

for i in range(0, num_of_blocks_to_add):
    block_to_add = next_block(previous_block)
    blockchain.append(block_to_add)
    previous_block = block_to_add
    print ("Block #{} has been added to the blockchain!".format(block_to_add.index))
    print ("Hash: {}\n".format(block_to_add.hash))    

For anyone in Python 3, just changed the line 14. Tested and it worked