Programming Blockchain Part 3: Python Programming Language

This guide covers programming blockchain part 3: python programming language with practical context and easy-to-follow details. Use it to understand the subject and apply the information confidently.

1. Programming blockchain part 1: C ++ programming language
2. Programming blockchain part 2: JavaScript programming language

In the previous two sections you know why C ++ and JavaScript are chosen to program blockchain. In addition to these two programming languages, Python is also a popular choice in blockchain programming. This article helps you understand the reason behind it.

Python Programming Language

1. How to install Python on Windows, macOS, Linux

Check out a simple 'hello world' program.

 print ('Hello, world!') 

Compare with C ++ 'hello world' program. It is much simpler.

So what about some more complicated things? Suppose we are adding two numbers and having results.

 num1 = 1.5 
 num2 = 6.3 
 sum = float (num1) + float (num2) 
 print ('The sum of {0} and {1} is {2}'. format (num1, num2, sum)) 

The result will be: Sum of 1. 5 and 6. 3 with 7. 8

So how to program an entire blockchain using Python? The following data and code are taken from the article written by Gerald Nash on Medium.

How to Create Blocks

Start by creating a block:

 Block class: 
 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 () 

Analyze the code

We start by entering the Hash library To use the SHA 256 Hash function (quite similar to JavaScript).

Like JavaScript, blocks have the following values:

1. Index
2. Timestamp
3. Data
4. Previous hash
5. Hash.

Next, assign hash values through a function, just like in JavaScript.

How to Create Genesis Blocks

Now, create Genesis blocks:

Enter Datetime As the current date.

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

Analyze the code

Enter datetime to set a timestamp.

The task now is to simply create the genesis blocks and manually assign it some data to operate. The previous hash value is '0' because it does not point to any other block.

How to Create the Rest of the Blocks

Now, determine how the next blocks will be created.

 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) 

Analyze the code

So, how do we determine the values of every piece of data inside each block?

1. The index block Is simply the index of the last block + 1.
2. Timestamp Is the current date and time.

Data of the block is a simple message: ' Hey!I'm block '.

Hash is being calculated using the previously called function.

And finally, all these values will be returned to the block.

How to Create Blockchain

To finish, create a blockchain.

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

 num_of_blocks_to_add = 15 

 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 # {} đã được thêm vào blockchain!". format (block_to_add.index) 
 print "Hash: {} n" .format (block_to_add.hash) 

Analyze the code

Start by creating the genesis block and set its value to ' Previous_block '.

Next, determine how many blocks are added. In this example, 15 blocks will be added.

Therefore, the extra block step will be repeated 15 times to add each block to the blockchain. Finally, the export of block numbers has been added to the blockchain through their index number, and the output of the hash is also exported.

This is the output:

Obviously in both Python and JavaScript, you can add more complex features like Proof Of Work. If you want to learn how to do that, you should look at Gerald Nash's article. But now, at least you know how to create a simple blockchain in Python.