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How to Implement Disjoint Set Union Find in Python
Implement a Disjoint Set Union-Find data structure using a Python dictionary for parent tracking, with path compression and connectivity checks.
class DisjointSet:
def __init__(self):
self.parent = {}
def find(self, x):
# Path compression
if self.parent[x] != x:
self.parent[x] = self.find(self.parent[x])
return self.parent[x]
def union(self, x, y):
# Initialize if not present
if x not in…Composable Predicates with the &, |, ~ Operators in Python
Define a reusable Predicate class that combines boolean checks with & (AND), | (OR), and ~ (NOT) operators.
class Predicate:
def __init__(self, func, name=None):
self.func = func
self.name = name or getattr(func, "__name__", "predicate")
def __call__(self, value):
return self.func(value)
def __and__(self, other):
return Predicate(lambda v: self(v) and other(v), f"({self.name} AN…Split Array Largest Sum in Python (Minimize Largest Subarray Sum)
Binary search + greedy check to split an array into k subarrays while minimizing the largest subarray sum.
def can_split(nums, k, max_sum):
subarrays = 1
current_sum = 0
for num in nums:
if current_sum + num <= max_sum:
current_sum += num
else:
subarrays += 1
current_sum = num
if subarrays > k:
return False
return True
def spli…Validate Sudoku Board Rows Columns and Boxes in Python
Validate a 9x9 Sudoku board by checking that each row, column, and 3x3 box contains the numbers 1 through 9 exactly once.
def validate_sudoku(board):
def is_valid_group(group):
return sorted(group) == list(range(1, 10))
def get_columns():
return [[board[r][c] for r in range(9)] for c in range(9)]
def get_boxes():
boxes = []
for box_row in range(0, 9, 3):
for box_col in range(0, 9,…Build a Python Utility That Verifies Backup Integrity Automatically
Automatically compute and verify SHA-256 checksums of backup files using a JSON manifest to detect missing or corrupted data.
import hashlib
import os
import json
def compute_checksum(filepath, algorithm='sha256'):
"""Compute checksum for the given file."""
hash_func = hashlib.new(algorithm)
with open(filepath, 'rb') as f:
for chunk in iter(lambda: f.read(4096), b''):
hash_func.update(chunk)
return hash_f…Find Broken Image References Across a Website in Python
Crawl internal pages of a website, collect all image source URLs, then check each with HEAD requests to report any that return HTTP 4xx or connection errors.
import requests
from urllib.parse import urljoin, urlparse
from bs4 import BeautifulSoup
from concurrent.futures import ThreadPoolExecutor, as_completed
def find_all_links(base_url, max_pages=50):
visited, to_visit = set(), {base_url}
while to_visit and len(visited) < max_pages:
url = to_visit.pop()
…How to Check SSL Certificate Expiry in Python
Connect to a host over TLS, extract the certificate's expiry date, and report days remaining using only the Python standard library.
import socket
import ssl
from datetime import datetime
def check_cert_expiry(hostname, port=443):
context = ssl.create_default_context()
with socket.create_connection((hostname, port), timeout=10) as sock:
with context.wrap_socket(sock, server_hostname=hostname) as tls_sock:
cert = tls_soc…How to Detect Unused Images in a Project with Python
A Python script that scans a website project folder, identifies all image files, and checks HTML/CSS/JS files to find which images are never referenced.
import os
import re
from pathlib import Path
def find_unused_images(project_path):
image_exts = {'.png', '.jpg', '.jpeg', '.gif', '.svg', '.webp'}
used_images = set()
all_images = set()
# Find all image files
for root, _, files in os.walk(project_path):
for file in files:
…How to Ping Multiple Hosts in Parallel with Python ThreadPoolExecutor
A parallel host-pinging script using ThreadPoolExecutor and subprocess to check connectivity across multiple addresses concurrently.
import subprocess
from concurrent.futures import ThreadPoolExecutor
from pathlib import Path
HOSTS = [
"google.com",
"github.com",
"stackoverflow.com",
"nonexistent.invalid",
"localhost",
]
def ping_host(host: str) -> str:
"""Ping a single host and return a status string."""
result = subp…How to Scan Open Ports on a Host with Python
A Python function that uses socket.connect_ex to check for open TCP ports on a given host within a range and returns a list of open ports.
import socket
def scan_ports(host, start_port, end_port):
open_ports = []
for port in range(start_port, end_port + 1):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(0.5)
result = sock.connect_ex((host, port))
if result == 0:
open_ports.app…How to Validate SSL Certificates for Multiple Domains in Python
A Python utility that checks SSL certificate expiry dates for a list of domains using the standard library ssl and socket modules.
import ssl
import socket
from datetime import datetime
def check_ssl_certificate(hostname: str, port: int = 443) -> dict:
"""Validate SSL certificate for a given hostname."""
context = ssl.create_default_context()
with socket.create_connection((hostname, port), timeout=5) as sock:
with context.wra…How to check Python files for common coding mistakes
Walks a directory tree parsing each .py file with ast, reporting empty functions, bare try blocks, too many parameters, and empty classes.
import ast
import os
import sys
def check_file(filepath):
try:
with open(filepath) as f:
code = f.read()
tree = ast.parse(code, filename=filepath)
except SyntaxError as e:
print(f"{filepath}: SyntaxError: {e.msg}")
return
issues = []
for node in ast.wal…Check Null Rate Threshold in PySpark DataFrame
This PySpark code checks the null rate of specified DataFrame columns against a threshold and returns violations.
from pyspark.sql import SparkSession
from pyspark.sql.functions import col, sum, count
def check_null_rate(df, threshold=0.2, columns=None):
"""
Check null rate for specified columns (or all) against a threshold.
Returns columns that exceed the threshold.
"""
cols = columns or df.columns
total…How to Validate Fact Table Grain Row Counts in Python
Validate fact table grain by checking dimension key references, unique grain combinations, duplicate rows, and dimension cardinality from a CSV file.
import csv
import hashlib
from pathlib import Path
def validate_fact_grain(fact_file: Path, expected_dim_keys: dict[str, set[str]]) -> dict:
"""
Validate fact table grain by checking each row's dimension keys exist
in expected dimension tables and row count consistency.
"""
dim_references = {}
…How to Mock open() in Python Using unittest.mock.patch
This code shows how to use unittest.mock.patch with mock_open to test a function that checks if a Git patch can be reverse-applied by reading file content.
import unittest
from unittest.mock import patch, mock_open
def apply_reverse_check(file_path, expected_patch):
"""
Check if a patch can be reverse-applied by comparing file content
with the expected patch's reverse result.
"""
try:
with open(file_path, "r") as f:
content = f.r…Python Script to Rotate a Leaked API Key
A checklist-driven Python script that scans a codebase for a leaked API key, replaces it with a new one, and prints a step-by-step rotation checklist.
#!/usr/bin/env python3
"""Checklist for rotating a leaked API key across a codebase."""
import re
from pathlib import Path
CHECKLIST = [
"Identify all files containing the leaked key",
"Generate a new key with sufficient entropy",
"Update the secret storage/CI environment variables",
"Replace the ol…How to Validate Data in Python with Typing Hints
Build a runtime validation helper that checks values against Python type hints like Optional, list, and basic types.
from typing import Any, Optional, Union, TypeVar, get_origin, get_args
T = TypeVar("T")
def validate(value: Any, expected_type: type) -> Optional[str]:
"""Returns an error message if value doesn't match expected_type, else None."""
# Handle Optional[...] types
origin = get_origin(expected_type)
if or…How to Implement the Abstract Factory Pattern in Python
Implements the Abstract Factory pattern to create families of related GUI objects (buttons, checkboxes) without specifying their concrete classes.
from abc import ABC, abstractmethod
class Button(ABC):
@abstractmethod
def render(self):
pass
class Checkbox(ABC):
@abstractmethod
def render(self):
pass
class WindowsButton(Button):
def render(self):
return "Rendering Windows-style button"
class WindowsCheckbox(Chec…How to implement stale-while-revalidate caching in Python
A Python cache wrapper that returns a stale cached value with a fallback flag when the upstream fetch fails, using TTL-based freshness checks.
import time
from functools import lru_cache
class CachedService:
def __init__(self, fetch_func, ttl=5):
self.fetch_func = fetch_func
self.ttl = ttl
self._cache = {}
self._timestamp = {}
def get(self, key):
now = time.time()
if key in self._cache and now - self…How to Validate Request Body JSON Against a Schema in Python
Build a lightweight schema validator to check required fields, types, string lengths, allowed values, and nested objects in a JSON request body.
import json
def validate_against_schema(data, schema, path=""):
errors = []
if not isinstance(data, dict):
errors.append(f"{path}: expected object, got {type(data).__name__}")
return errors
for field, rules in schema.items():
field_path = f"{path}.{field}" if path else field
…Redis Leaky Bucket Rate Limiting Mock in Python
Simulates a Redis-backed leaky bucket rate limiter using a local class with continuous leaking and token capacity checks.
import time
from collections import deque
class LeakyBucket:
def __init__(self, capacity, leak_rate):
self.capacity = capacity
self.leak_rate = leak_rate
self.water = 0.0
self.timestamp = time.time()
self.history = deque()
def allow(self):
current = time.time(…How to Mock a Liveness Check and Restart a Process in Python
Simulate a failing process and restart it after a liveness check fails, using a mock class and a liveness loop.
import subprocess
import sys
import time
import os
class ProcessMock:
def __init__(self, name, fail_after_seconds=3):
self.name = name
self.fail_after = fail_after_seconds
self.start_time = None
self.is_running = False
def start(self):
self.start_time = time.time()
…How to Check Uptime with a Synthetic HTTP Mock in Python
Run a mock HTTP server locally and probe it with urllib to measure synthetic uptime and response times, perfect for testing monitoring logic without external dependencies.
import http.server
import threading
import time
import urllib.request
class MockHandler(http.server.BaseHTTPRequestHandler):
def do_GET(self):
if self.path == "/health":
self.send_response(200)
self.send_header("Content-Type", "application/json")
self.end_headers()
…Check Covariate Balance in Python
Compute standardized mean differences and KS tests to check covariate balance between treatment and control groups in Python.
import numpy as np
from scipy import stats
def balance_check(treatment, covariate):
"""Check covariate balance between treatment and control groups."""
treat_vals = covariate[treatment == 1]
control_vals = covariate[treatment == 0]
# Standardized mean difference
pooled_std = np.sqrt((np.var(t…Browse by section
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