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How to Build a Two-Way Dictionary in Python
Implement a BiDict class that supports both forward key-to-value and reverse value-to-key lookups with a simple add, delete, and update API.
class BiDict:
def __init__(self, data=None):
self.forward = {}
self.backward = {}
if data:
self.update(data)
def update(self, data):
for key, value in data.items():
self[key] = value
def __setitem__(self, key, value):
self.forward[key] = val…Find Longest Consecutive Sequence in Python
Find the length of the longest consecutive elements sequence in an unsorted array using a set for O(n) lookups.
def longest_consecutive_length(nums):
num_set = set(nums)
longest = 0
for num in num_set:
if num - 1 not in num_set:
current = num
current_streak = 1
while current + 1 in num_set:
current += 1
current_streak += 1
…How to Build a Mock Route53 DNS API in Python
Create a mock DNS API server in Python that simulates Route53 record lookups and updates using the standard library.
import json
from http.server import BaseHTTPRequestHandler, HTTPServer
from urllib.parse import urlparse, parse_qs
class DNSUpdateHandler(BaseHTTPRequestHandler):
records = {"example.com": "1.2.3.4"}
def do_GET(self):
domain = parse_qs(urlparse(self.path).query).get("domain", [""])[0]
if dom…How to Build a Bloom Filter to Reduce Cache Misses in Python
Implement a probabilistic Bloom filter in Python that lets a cache quickly determine which keys are definitely not present, reducing expensive source lookups on cache misses.
import hashlib
import random
class BloomFilter:
def __init__(self, size=100, num_hashes=3):
self.size = size
self.num_hashes = num_hashes
self.bit_array = [0] * size
def _hashes(self, item):
result = []
for i in range(self.num_hashes):
hash_value = int(hash…How to Implement a Negative Cache with TTL in Python
This code provides a TTL mock cache that stores negative results (cache misses) for a short time to reduce repeated lookups of missing keys.
from time import time, sleep
class TTLMockCache:
def __init__(self, ttl_seconds=5):
self.ttl = ttl_seconds
self.store = {}
self.negative_cache = {}
def get(self, key):
now = time()
if key in self.store:
value, expires_at = self.store[key]
if exp…How to implement OCSP stapling mock in Python
Simulate OCSP stapling with a caching mechanism that mocks certificate status lookups for TLS handshake validation.
import hashlib
import time
class OCSPStapler:
def __init__(self, cert_serial: str, issuer_hash: str):
self.cert_serial = cert_serial
self.issuer_hash = issuer_hash
self.cache = {}
def _mock_query_ocsp(self, serial: str) -> dict:
"""Simulate OCSP responder lookup."""
di…How to mock DNS CAA record lookups in Python
Parse and filter DNS CAA records with a mock lookup function, demonstrating how certificate authorities validate domain authorization.
import dnslib
def parse_caa_record(record_string):
"""Parse a DNS CAA record string into its components."""
parts = record_string.split()
flags = int(parts[0])
tag = parts[1]
value = parts[2]
return flags, tag, value
def mock_caa_lookup(domain, caa_records):
"""Mock DNS CAA lookup that re…Browse by section
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