ソフトウェアエンジニアの技術ブログ：Software engineer tech blog

import hashlib
import json
from datetime import datetime
import random

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

    def calculate_hash(self):
        block_dict = self.__dict__
        if 'hash' in block_dict:
            del block_dict['hash']
        block_string = json.dumps(block_dict, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()

class Blockchain:
    def __init__(self):
        self.chain = []              # A list that holde the blocks of the blockchain
        self.unconfirmed_data = []   # A list of new data or transactions
        self.validators = {}         # A dictionary where each validator is recoded
        self.staked_tokens = {}      # A dictionary that holds the amount of staked tokens for each validator.
        self.minimum_stake = 500     # The minimum amout of tokens a validator must stake to participate in the network
        self.create_genesis_block()  # The genesis block is the first block in the blockchain.

    def create_genesis_block(self):
        genesis_block = Block(0, None, str(datetime.now()), "Genesis Block", None)
        self.chain.append(genesis_block)    
    
    def last_block(self):
        return self.chain[-1]

    def add_data(self, new_data):
        self.unconfirmed_data.append(new_data)

    def add_validator(self, validator, stake):
        if stake >= self.minimum_stake:
            self.staked_tokens[validator] = stake
            self.validators[validator] = True
        else: 
            print(f"{validator} does not meet the minimum stake requirement.")
    
    def select_validator(self):
        total_stake = sum(self.staked_tokens.values())
        selected_validator = None
        while selected_validator == None:
            pick = random.uniform(0, total_stake)
            print(pick)
            current = 0
            for validator, stake in self.staked_tokens.items():
                print(validator, stake)
                current += stake
                if current > pick:
                    selected_validator = validator
                    break
        return selected_validator

    def create_block(self, validator):
        if not self.unconfirmed_data:
            return False
        
        last_block = self.last_block()
        new_block = Block(index=last_block.index + 1,
                        previous_hash=last_block.hash,
                        timestamp=str(datetime.now()),
                        data=self.unconfirmed_data,
                        validator=validator)
        self.chain.append(new_block)
        self.unconfirmed_data = []
        return new_block.index

    def display_chain(self):
        for block in self.chain:
            print(f"Block {block.__dict__}")


# sample
blockchain = Blockchain()

blockchain.add_validator("A", 2000)
blockchain.add_validator("B", 50)
blockchain.add_validator("C", 650)
blockchain.add_validator("D", 30)
blockchain.add_validator("E", 100000)
blockchain.add_validator("F", 25)

blockchain.add_data("Alice send Bob 200 coin")
blockchain.add_data("Bob send Chen 2000 coin")

selected_validator = blockchain.select_validator()
print(f"Validator selected: {selected_validator}")

blockchain.create_block(selected_validator)
blockchain.display_chain()

$ python3 main.py
B does not meet the minimum stake requirement.
D does not meet the minimum stake requirement.
F does not meet the minimum stake requirement.
27576.935798973213
A 2000
C 650
E 100000
Validator selected: E
Block {‘index’: 0, ‘previous_hash’: None, ‘timestamp’: ‘2024-11-27 03:59:33.053116’, ‘data’: ‘Genesis Block’, ‘validator’: None, ‘hash’: ‘df536d1db7e82ccd6f51e244928263163cd36b9724c4fdb8df77a72923dca021’}
Block {‘index’: 1, ‘previous_hash’: ‘df536d1db7e82ccd6f51e244928263163cd36b9724c4fdb8df77a72923dca021’, ‘timestamp’: ‘2024-11-27 03:59:33.053659’, ‘data’: [‘Alice send Bob 200 coin’, ‘Bob send Chen 2000 coin’], ‘validator’: ‘E’, ‘hash’: ‘120255b4707e317e599eff7183b73e31bfc691d71ca987d8186a854c91e5d1bd’}

うーん、なるほどな〜 というところか…

The uniform() method returns a random floating number between the two specified numbers (both included).

import random

print(random.uniform(20, 30))

$ python3 test.py
25.547661293351773
$ python3 test.py
27.825416674846192

mydict = {"mike":50, "peter":30, "john":75}
total_score = sum(mydict.values())
print(total_score)

$ python3 test.py
155

import json
class MyClass:
    def __init__(self, a, b):
        self.group = []
        self.a = a
        self.b = b

    def add(self):
        c = self.a + self.b
        self.group.append(c)
        print(self.group)

obj = MyClass(2, 4)
obj.add()
obj.add()

$ python3 test.py
[6]
[6, 6]

json.dumpする際に、sort_keysをTrueとすることで、dictionallyのkeyでソートする

import json
class MyClass:
    def __init__(self, a, c, b):
        self.a = a
        self.c = c
        self.b = b

obj = MyClass(2, 4, 6)

string = json.dumps(obj.__dict__)
print(string)

string = json.dumps(obj.__dict__, sort_keys=True)
print(string)

$ python3 test.py
{“a”: 2, “c”: 4, “b”: 6}
{“a”: 2, “b”: 6, “c”: 4}

なるほど、これで下のコードが何をやってるのか理解できたわ

import hashlib
import json
from datetime import datetime
import random

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

    def calculate_hash(self):
        block_dict = self.__dict__
        if 'hash' in block_dict:
            del block_dict['hash']
        block_string = json.dumps(block_dict, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()

__dict__はオブジェクトが持つ属性とその値を格納する辞書を返す特殊属性
モジュール、クラス、インスタンスなどで参照可能

class MyClass:
    def __init__(self, x, y):
        self.x = x
        self.y = y

obj = MyClass(2, 4)
print(obj.__dict__)

$ python3 test.py
{‘x’: 2, ‘y’: 4}

追加、更新、削除も可能

class MyClass:
    def __init__(self, x, y):
        self.x = x
        self.y = y

obj = MyClass(2, 4)
print(obj.__dict__)

obj.__dict__['z'] = 3
print(obj.__dict__)

obj.__dict__['x'] = 10
print(obj.__dict__)

del obj.__dict__['y']
print(obj.__dict__)

$ python3 test.py
{‘x’: 2, ‘y’: 4}
{‘x’: 2, ‘y’: 4, ‘z’: 3}
{‘x’: 10, ‘y’: 4, ‘z’: 3}
{‘x’: 10, ‘z’: 3}

dictはdictionallyの略ですね。__init__と__dict__が同時に出ると、やや混乱しましたが、使い方を理解すれば合点行きます。

initがコンストラクターとなり、selfはオブジェクト自身を表す

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def share_self(self):
        print("名前:", self.name)
        print("年齢:", self.age, '歳')

person_1 = Person('田中', 18)
person_2 = Person('山田', 20)

person_1.share_self()
person_2.share_self()

$ python3 test.py
名前: 田中
年齢: 18 歳
名前: 山田
年齢: 20 歳

エンコードしたテキストをsha256でハッシュ化

import hashlib

text = "bbb"
encode_string = text.encode()
print(hashlib.sha256(encode_string).hexdigest())

$ python3 test.py
3e744b9dc39389baf0c5a0660589b8402f3dbb49b89b3e75f2c9355852a3c677