Reference library

System design patterns

Sharding, load balancing, CAP tradeoffs, and scaling patterns — interview and production ready.

3 matches

Create a Data Helper Class in Python

A reusable DataHelper class that saves and loads JSON and CSV files from a configurable base directory, with automatic header detection for CSV.

data-helper json csv

Python

import json
import csv
from pathlib import Path

class DataHelper:
    def __init__(self, base_path="."):
        self.base_path = Path(base_path)
        self.base_path.mkdir(exist_ok=True)

    def save_json(self, data, filename):
        path = self.base_path / filename
        with open(path, "w") as f:
          …

15 0 Open

System design patterns easy

How to Build a Weighted Random Load Balancer in Python

A Python load balancer mock that distributes requests across servers based on configurable weights using a cumulative weighted random selection algorithm.

python how build

Python

import random
from collections import Counter

SERVERS = {
    "server-a": 50,
    "server-b": 30,
    "server-c": 20,
}


def weighted_random_server(servers: dict[str, int]) -> str:
    """Select a server based on its weight (higher weight = more likely)."""
    total_weight = sum(servers.values())
    rand = random.…

13 0 Open

System design patterns medium

Singleton Config Loader in Python with Caution

Implements a singleton config loader in Python that reads JSON config files, but demonstrates the hidden gotcha of shared state across instances.

singleton config design-patterns

Python

import json
from pathlib import Path

class ConfigLoader:
    _instance = None

    def __new__(cls, *args, **kwargs):
        if cls._instance is None:
            cls._instance = super().__new__(cls)
        return cls._instance

    def __init__(self, config_file="config.json"):
        if not hasattr(self, "loaded…

12 0 Open

Browse by section

Each section groups closely related Python snippets.