aunyks/snakecoin.py

rogel-appdev · 2017-08-06T23:47:55Z

Hello there,

I am getting the below error:

blockchain = [create_genesis_block()]

NameError: name 'create_genesis_block' is not defined

I am using Python 3.6.0 and IDLE 3.6.0

Thanks in advance

heimdallrj · 2017-08-08T08:48:38Z

JS/nodejs version

const sha256 = require('js-sha256');

// Define the Block Class
class Block {
  constructor(index, data, previousHash) {
    this.index = index;
    this.timestamp = new Date();
    this.data = data;
    this.previousHash = previousHash;
    this.hash = this.generateHash();

  }

  generateHash() {
    return sha256.hex(`${this.index}${this.timestamp}${this.data}${this.previousHash}`);
  }
}

// Create genesis block
function createGenesisBlock() {
  return new Block(0, 'Genesis Block', '0');
}

// Create all other blocks
function createNextBlock(previousBlock, data=null) {
  const index = previousBlock.index + 1;
  const previousHash = previousBlock.hash;
  return new Block(index, data, previousHash);
}

// Demo
// Create the Blockchain
const blockchain = [createGenesisBlock()];
let previousBlock = blockchain[0];

for (let i=0; i<20; i++) {
  const block = createNextBlock(previousBlock);
  blockchain.push(block);
  previousBlock = block;

  console.log(`Block #${block.index} has been added to the blockchain!.`);
  console.log(`Hash: ${block.hash}\n`);
}

wowkin2 · 2017-08-08T11:33:48Z

I think that index should be autoincremented to avoid case there are blocks with the same index.

wowkin2 · 2017-08-08T11:41:52Z

Made some updates (see my gist).
Created separate class for blockchain, as result got simple interface to create blocks and retrieve information about them.
In future, we can add there more functionality there.

wowkin2 · 2017-08-08T11:51:47Z

@aunyks, found other gist-files about Snakecoin, maybe it is good idea to join them in a single gist or create a repo for that?

ssabat · 2017-09-14T00:41:30Z

I tried js/nodejs version on my Mac.

I saved code in a file called snakecoin.js. Then, I did following.

brew install node ( it will install dependency icu4c )
npm install js-sha256
node snakecoin.js

20 blocks were created and added. Last few lines of output are:

..............
...................
Block #18 has been added to the blockchain!.
Hash: af71818c33d461d5ccb58902df4ac56b5774ebf533e43fd3fe18d66a44073f8c

Block #19 has been added to the blockchain!.
Hash: 650fedbb88c13e3a2cb45e5a35b08c8d4ac907137cd8d810a09a2c53815943b8

Block #20 has been added to the blockchain!.
Hash: 7317a8c58a031c23e032e947c54f28dcac9b076274992d7b486d6558d35ff86f

Thanks @thinkholic for sharing the code.

Winand · 2017-10-30T11:38:05Z

@joeblankenship1 you can encode all data at once to utf-8 like this:

sha.update((str(self.index) + 
            str(self.timestamp) + 
            str(self.data) + 
            str(self.previous_hash)).encode())

Or we can append data chunks separately: https://docs.python.org/3/library/hashlib.html#hashlib.hash.update

sha.update(str(self.index).encode())
sha.update(str(self.timestamp).encode())
sha.update(str(self.data).encode())
sha.update(str(self.previous_hash).encode())

----Python 3

JohnStuartRutledge · 2017-11-07T16:37:38Z

In case it helps anyone, here is the working Python 3 version I got working that includes a few tweaks like encoding the class attributes to utf-8.

Thanks to OP for the tutorial!

from datetime import datetime
import hashlib as hasher


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 __str__(self):
        return 'Block #{}'.format(self.index)

    def hash_block(self):
        sha = hasher.sha256()
        seq = (str(x) for x in (
               self.index, self.timestamp, self.data, self.previous_hash))
        sha.update(''.join(seq).encode('utf-8'))
        return sha.hexdigest()


def make_genesis_block():
    """Make the first block in a block-chain."""
    block = Block(index=0,
                  timestamp=datetime.now(),
                  data="Genesis Block",
                  previous_hash="0")
    return block


def next_block(last_block, data=''):
    """Return next block in a block chain."""
    idx = last_block.index + 1
    block = Block(index=idx,
                  timestamp=datetime.now(),
                  data='{}{}'.format(data, idx),
                  previous_hash=last_block.hash)
    return block


def test_code():
    """Test creating chain of 20 blocks."""
    blockchain = [make_genesis_block()]
    prev_block = blockchain[0]
    for _ in range(0, 20):
        block = next_block(prev_block, data='some data here')
        blockchain.append(block)
        prev_block = block
        print('{} added to blockchain'.format(block))
        print('Hash: {}\n'.format(block.hash))


# run the test code
test_code()

cleverlight · 2017-11-13T09:04:54Z

@aunyks please could you include a licence in your code because I'd like to reuse it? Alternatively might you consider putting a default licence on all your gists (e.g. https://gist.github.com/rwaldron/1056460) please?

benrhine · 2017-12-15T20:47:09Z

I have ported this code to both Java and Groovy. Additionally if you want to change block implementation you can edit the code to choose between a pure Java implementation or the preferred Guava implementation.

Groovy Version:
https://github.com/benrhine/GroovySnakeCoin

Java 8 Version:
https://github.com/benrhine/JavaSnakeCoin

briansb · 2018-02-27T20:54:05Z

Thanks @JohnStuartRutledge ! Works great!

rajfal · 2018-02-28T00:23:00Z

Thanks to @aunyks @JohnStuartRutledge
I'm using Python 3.6, however something was not working out and I was getting:
...
Block #5 added to blockchain
Hash: <bound method Block.hash_block of <main.Block object at 0x7efe6c902588>>

It appears that the line:
print('Hash: {}\n'.format(block.hash))

needs to be
print('Hash: {}\n'.format(block.hash()))

in order to obtain:
Block #5 added to blockchain
Hash: 80963e3493ffed59bb9ec6653621328d53dfc81994ae15f2c29b29eb7d0bb1c1

block.hash gives us the method object itself,
whereas, we want to actually call block.hash() instead

aishoot · 2018-02-28T07:00:37Z

great

koshikraj · 2018-03-16T13:54:27Z

Similar implementation and packaged with tests.
https://github.com/koshikraj/justblockchain

Also, check out the extended implementation with block validation with server interface.
https://github.com/koshikraj/pynaivechain

mega-byte2600 · 2018-04-29T01:02:55Z

Thx to all very good stuff:

Block #20 added to blockchain
Hash: 2c4fd089fd70c17ec4eb73b2555cada39f2d8d98b45e74bc3dea99b550a9c6a4 :-)

AjayZinngg · 2018-07-18T13:25:20Z

@rogel-appdev were you able to resolve the issue? I am facing the same one.

AjayZinngg · 2018-07-18T14:18:17Z

I found the solution.
Add import statements to your files.

Gothamv · 2018-08-01T17:29:05Z

Python 3

import hashlib as hasher
import datetime as date

class Block: # Defining what a GitCoin consists of
    def __init__(self,index,timeStamp,data,previousHash):
        self.index = index
        self.timeStamp = timeStamp
        self.data = data
        self.previousHash = previousHash
        self.hash = self.hashBlock()
    
    def hashBlock(self):
        sha = hasher.sha256() # sha256 is a hashing algorithm
        sha.update(str(self.index).encode('utf-8') + str(self.timeStamp).encode('utf-8') + str(self.data).encode('utf-8') + str(self.previousHash).encode('utf-8'))
        return sha.hexdigest() # returns the combined hash value in Hexadecimals

def createGenesisBlock(): # Pre-Defining a block with index 0 and an arbitrary previous hash 
    return Block(0, date.datetime.now, "Genesis Block", 0)

def createNextBlock(prevBlock): # Creating all the later blocks in the blockchain
    currIndex = prevBlock.index + 1
    currTimeStamp = date.datetime.now()
    currData = "Block" + str(currIndex)
    currHash = prevBlock.hash
    return Block(currIndex, currTimeStamp, currData, currHash)

blockChain = [createGenesisBlock()] # Creating the BlockChain
prevBlock = blockChain[0] # Adding the Genesis block

blocksToCreate = 20 # No. of blocks to be added after the Genesis Block

for i in range(0,blocksToCreate):
    blockToAdd = createNextBlock(prevBlock)
    blockChain.append(blockToAdd)
    prevBlock = blockToAdd
    print("Block %s has been added to the blockchain!" % (blockToAdd.index))
    print("Hash: %s\n" % (blockToAdd.hash))

epogrebnyak · 2018-08-02T08:48:20Z

Can we do better than this? Repeated code is never a good sign.

str(self.index).encode('utf-8') + str(self.timeStamp).encode('utf-8') + str(self.data).encode('utf-8') + str(self.previousHash).encode('utf-8')

For example:

def encode(x):
     return str(x).encode('utf-8')

def concat(elements: list):
     return ''.join([encode(x) for x in elements])

# the expression above becomes
concat([self.index, self.timeStamp, self.data, self.previousHash])

Or is this loosing some readbility?

schaefd · 2018-10-18T14:19:18Z

In case it helps anyone, here is the working Python 3 version I got working that includes a few tweaks like encoding the class attributes to utf-8.

Thanks to OP for the tutorial!

from datetime import datetime
import hashlib as hasher


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 __str__(self):
        return 'Block #{}'.format(self.index)

    def hash_block(self):
        sha = hasher.sha256()
        seq = (str(x) for x in (
               self.index, self.timestamp, self.data, self.previous_hash))
        sha.update(''.join(seq).encode('utf-8'))
        return sha.hexdigest()


def make_genesis_block():
    """Make the first block in a block-chain."""
    block = Block(index=0,
                  timestamp=datetime.now(),
                  data="Genesis Block",
                  previous_hash="0")
    return block


def next_block(last_block, data=''):
    """Return next block in a block chain."""
    idx = last_block.index + 1
    block = Block(index=idx,
                  timestamp=datetime.now(),
                  data='{}{}'.format(data, idx),
                  previous_hash=last_block.hash)
    return block


def test_code():
    """Test creating chain of 20 blocks."""
    blockchain = [make_genesis_block()]
    prev_block = blockchain[0]
    for _ in range(0, 20):
        block = next_block(prev_block, data='some data here')
        blockchain.append(block)
        prev_block = block
        print('{} added to blockchain'.format(block))
        print('Hash: {}\n'.format(block.hash))


# run the test code
test_code()

Thanks OP! And to JohnStuartRutledge. This worked for me.

nobody5050 · 2018-10-29T15:49:02Z

Uhh how would I create a wallet for this file

MALLI7622 · 2019-08-24T04:51:44Z

I modified line 15 as below and it worked just fine:

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'))

:Thank you +1:

Anas-Aymen · 2019-12-08T10:22:59Z

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 !

suncle1993 · 2021-06-23T11:52:55Z

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()

Chike-O-IT · 2022-04-08T20:03:32Z

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!

goesbyabhi · 2022-04-28T18:53:08Z

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

aunyks/snakecoin.py

rogel-appdev commented Aug 6, 2017

heimdallrj commented Aug 8, 2017

wowkin2 commented Aug 8, 2017

wowkin2 commented Aug 8, 2017

wowkin2 commented Aug 8, 2017

ssabat commented Sep 14, 2017 •

edited

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Winand commented Oct 30, 2017 •

edited

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JohnStuartRutledge commented Nov 7, 2017

cleverlight commented Nov 13, 2017

benrhine commented Dec 15, 2017

briansb commented Feb 27, 2018

rajfal commented Feb 28, 2018

aishoot commented Feb 28, 2018

koshikraj commented Mar 16, 2018

mega-byte2600 commented Apr 29, 2018

AjayZinngg commented Jul 18, 2018

AjayZinngg commented Jul 18, 2018

Gothamv commented Aug 1, 2018 •

edited

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epogrebnyak commented Aug 2, 2018 •

edited

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schaefd commented Oct 18, 2018

nobody5050 commented Oct 29, 2018

MALLI7622 commented Aug 24, 2019

Anas-Aymen commented Dec 8, 2019

suncle1993 commented Jun 23, 2021

Chike-O-IT commented Apr 8, 2022

goesbyabhi commented Apr 28, 2022

	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)

aunyks/snakecoin.py

rogel-appdev commented Aug 6, 2017

heimdallrj commented Aug 8, 2017

wowkin2 commented Aug 8, 2017

wowkin2 commented Aug 8, 2017

wowkin2 commented Aug 8, 2017

ssabat commented Sep 14, 2017 • edited Loading

Winand commented Oct 30, 2017 • edited Loading

JohnStuartRutledge commented Nov 7, 2017

cleverlight commented Nov 13, 2017

benrhine commented Dec 15, 2017

briansb commented Feb 27, 2018

rajfal commented Feb 28, 2018

aishoot commented Feb 28, 2018

koshikraj commented Mar 16, 2018

mega-byte2600 commented Apr 29, 2018

AjayZinngg commented Jul 18, 2018

AjayZinngg commented Jul 18, 2018

Gothamv commented Aug 1, 2018 • edited Loading

Python 3

epogrebnyak commented Aug 2, 2018 • edited Loading

schaefd commented Oct 18, 2018

nobody5050 commented Oct 29, 2018

MALLI7622 commented Aug 24, 2019

Anas-Aymen commented Dec 8, 2019

suncle1993 commented Jun 23, 2021

Chike-O-IT commented Apr 8, 2022

goesbyabhi commented Apr 28, 2022

ssabat commented Sep 14, 2017 •

edited

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Winand commented Oct 30, 2017 •

edited

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Gothamv commented Aug 1, 2018 •

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epogrebnyak commented Aug 2, 2018 •

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