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

### 非同期処理とは？
あるタスクが終了するのを待っている間、別のタスクを実行すること

$ pip3 install aiohttp

import datetime
import aiohttp
import asyncio

start = datetime.datetime.now()

def log(message):
    print(f'{(datetime.datetime.now() - start).seconds}秒経過', message)

async def fetch(session, url):
    """ 非同期にURLからデータを取得 """
    print(f"Fetching {url}")
    async with session.get(url) as response:
        return await response.text()

async def main():
    log("タスク開始")
    urls = [
        "http://google.com",
        "http://qiita.com",
        "https://www.python.org/",
        "https://www.mozilla.org/en-US/",
        "https://html.spec.whatwg.org/multipage/",
        "https://www.w3.org/TR/css/",
        "https://ecma-international.org/",
        "https://www.typescriptlang.org/",
        "https://www.oracle.com/jp/java/technologies/",
        "https://www.ruby-lang.org/ja/",
        "https://www.postgresql.org/",
        "https://www.mysql.com/jp/",
        "https://docs.djangoproject.com/ja/5.0/",
        "https://spring.pleiades.io/projects/spring-boot",
        "https://rubyonrails.org/"
        "https://firebase.google.com/?hl=ja",
        "https://go.dev/",
        "https://nodejs.org/en"
    ]

    async with aiohttp.ClientSession() as session:
        tasks = [fetch(session, url) for url in urls]

        print("Starting tasks...")

        print("Tasks are running in the background...")

        results = await asyncio.gather(*tasks)

        for result in results:
            print(result[:100])

    log("task finished")

if __name__ == "__main__":
    asyncio.run(main())

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…