Python代码构建小型区块链DogCoin（狗币）

本文介绍了如何使用python构建一个小型的区块链技术，使用Python2.7实现，代码不到50行。

这个简单的区块链。这将被称为DogCoin（狗币）。

（一）定义区块链的块结构。

像比特币一样，我们的DogCoin每个区块将包括作为区块的索引的哈希值，时间戳，数据以及前一个块的哈希值和新的哈希值。如下图：

index

timestamp

data

previous_hash

hash

Python代码：

import hashlibas 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 hash_block(self):

sha = hasher.sha256()

sha.update(str(self.index) +

str(self.timestamp) +

str(self.data) +

str(self.previous_hash))

return sha.hexdigest()

（二）创建创世区块。

如前所述，每个块都需要上一个块的信息。但是这就出现了一个问题：区块链中的第一个区块，也就是“创世区块”，如何创建？

按照模块化原则，我们将创建一个函数，只需返回一个创世区块，该区块的索引为0，它在“previous hash”参数中具有任意数据值和任意值。

如下图：

Index：0

timestamp

Data：Genesis Block

previous_hash

hash

Python代码：

import datetime as date

def create_genesis_block():

# Manually construct a block with

# index zero and arbitrary previous hash

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

（三）创建后续区块。

我们需要一个新的函数来生成区块链中的后续区块。该函数将链中的前一个区块作为参数，创建要生成的区块的数据，并返回具有其相应数据的新块。新产生的区块会存储先前区块中的哈希值，区块链的完整性随着每个新的区块而增加。这个哈希链作为加密证明，有助于确保一旦新区块被添加到区块链中，它不能被替换或删除。

如下图：

Index：2

timestamp

Data：Hey! I'm block 2

previous_hash

hash

Python代码：

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)

（四）创建（组装）我们的区块链DogCoin。

区块链其实就是一个将普通指针换成哈希指针的链表，所以每个区块不仅包含了上一个区块的地址，还包括了上一个区块的哈希值。

列表的第一个元素是创世区块，然后需要添加后续区块。本例中，我们只添加了10个新的块，用for循环搞定。

如下图：

后续区块（4）

后续区块（3）

后续区块（2）

创世区块（1）

Python代码：

# Create theblockchain and add the genesis block

blockchain = [create_genesis_block()]

previous_block =blockchain[0]

# How manyblocks should we add to the chain

# after thegenesis block

num_of_blocks_to_add= 20

# Add blocks tothe 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 blockchain!".format(block_to_add.index)

print "Hash:{}\n".format(block_to_add.hash)

（五）打印区块链DogCoin的每个块！

我们的区块链生效了！

完整Python.代码如下：（python 2.7 idle）

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 hash_block(self):
sha = hasher.sha256()
sha.update(str(self.index) +
str(self.timestamp) +
str(self.data) +
str(self.previous_hash))
return sha.hexdigest()

import datetime as date

def create_genesis_block():
# Manually construct a block with
# index zero and arbitrary previous hash
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)

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

#Print genesis block
print "DogCoin"
print "---------------"
print "block index: {}".format(blockchain[0].index)
print "timestamp: {}".format(blockchain[0]. timestamp)
print "data: {}".format(blockchain[0]. data)
print "previous_hash: {}".format(blockchain[0]. previous_hash)
print "hash: {}\n".format(blockchain[0].hash)
print "---------------"

# How many blocks should we add to the chain
# after the genesis block
num_of_blocks_to_add = 10

# 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 blockchain!".format(block_to_add.index)
#print "Hash: {}\n".format(block_to_add.hash)
print "DogCoin"
print "---------------"
print "block index: {}".format(block_to_add.index)
print "timestamp: {}".format(block_to_add. timestamp)
print "data: {}".format(block_to_add. data)
print "previous_hash: {}".format(block_to_add. previous_hash)
print "hash: {}\n".format(block_to_add.hash)

print "---------------"

演示输出：

DogCoin

---------------

block index: 0

timestamp: 2018-03-15 13:59:12.750000

data: Genesis Block

previous_hash: 0

hash:978123c9edd1b41d5e35ce5126169cbd9f6f63efbc538b4d9ca63bb26da1a9b1

---------------

DogCoin

---------------

block index: 1

timestamp: 2018-03-15 13:59:12.828000

data: Hey! I'm block 1

previous_hash: 978123c9edd1b41d5e35ce5126169cbd9f6f63efbc538b4d9ca63bb26da1a9b1

hash:0de84484d23722cde7987a9dbe4ed0af9e415679888328fc3b9c069827727cfa

---------------

DogCoin

---------------

block index: 2

timestamp: 2018-03-15 13:59:12.906000

data: Hey! I'm block 2

previous_hash: 0de84484d23722cde7987a9dbe4ed0af9e415679888328fc3b9c069827727cfa

hash:7c0ce5d65626e4af2907ef6c8acfe05e9b8c39dcd5229583c0d4bc4f3d66a775

---------------

DogCoin

---------------

block index: 3

timestamp: 2018-03-15 13:59:12.984000

data: Hey! I'm block 3

previous_hash: 7c0ce5d65626e4af2907ef6c8acfe05e9b8c39dcd5229583c0d4bc4f3d66a775

hash:c1b7d949eea10af88659713b6145bd5069221d8fd49b337be8a8780684e0a16f

---------------

DogCoin

---------------

block index: 4

timestamp: 2018-03-15 13:59:13.078000

data: Hey! I'm block 4

previous_hash: c1b7d949eea10af88659713b6145bd5069221d8fd49b337be8a8780684e0a16f

hash:4915c65e6dc42d18cdd5489f458181f746aefafd7bc8b43e8c47c68dd0c90998

---------------

DogCoin

---------------

block index: 5

timestamp: 2018-03-15 13:59:13.156000

data: Hey! I'm block 5

previous_hash: 4915c65e6dc42d18cdd5489f458181f746aefafd7bc8b43e8c47c68dd0c90998

hash:95f61d76cabcf80e0ee3549ae88aa96f7b40e76f487ab1baa4ce0dee79fefbe8

---------------

DogCoin

---------------

block index: 6

timestamp: 2018-03-15 13:59:13.250000

data: Hey! I'm block 6

previous_hash: 95f61d76cabcf80e0ee3549ae88aa96f7b40e76f487ab1baa4ce0dee79fefbe8

hash:3206120a85d02a7b2b3ab85188913db304e6929141b0e4956a5ab65e21e508fe

---------------

DogCoin

---------------

block index: 7

timestamp: 2018-03-15 13:59:13.343000

data: Hey! I'm block 7

previous_hash: 3206120a85d02a7b2b3ab85188913db304e6929141b0e4956a5ab65e21e508fe

hash:54c4229a20dbe5e014b930eb31438c84bc6732240d023c8016dc17ad7b1b0287

---------------

DogCoin

---------------

block index: 8

timestamp: 2018-03-15 13:59:13.421000

data: Hey! I'm block 8

previous_hash: 54c4229a20dbe5e014b930eb31438c84bc6732240d023c8016dc17ad7b1b0287

hash:27d4561bd21fd36a794926139de39a3ea32ced70ac19e644544884ea923d418f

---------------

DogCoin

---------------

block index: 9

timestamp: 2018-03-15 13:59:13.500000

data: Hey! I'm block 9

previous_hash: 27d4561bd21fd36a794926139de39a3ea32ced70ac19e644544884ea923d418f

hash:143821446e2ccc4d7695242a591e0cd69f689a4b5f3c4c861c736deb8e5bee52

---------------

DogCoin

---------------

block index: 10

timestamp: 2018-03-15 13:59:13.578000

data: Hey! I'm block 10

previous_hash: 143821446e2ccc4d7695242a591e0cd69f689a4b5f3c4c861c736deb8e5bee52

hash:1a66358fb32db223a2f998061e3bc90354b0ddb8d2c3a013cc86c63060c5c547

---------------

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