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How to Implement a Trampoline for Tail Recursion in Python
This code implements a trampoline decorator that converts tail-recursive functions into iterative loops, allowing deep recursion without hitting Python's recursion limit.
def trampoline(fn):
"""Convert a tail-recursive function into an iterative loop."""
def wrapper(*args, **kwargs):
result = fn(*args, **kwargs)
while callable(result):
result = result()
return result
return wrapper
@trampoline
def factorial(n, acc=1):
"""Tail-recursi…How to Invalidate Cache When Arguments Change in Python
A memoization decorator that caches function results keyed by arguments, automatically invalidating when inputs change.
from functools import wraps
def memoize(func):
cache = {}
@wraps(func)
def wrapper(*args, **kwargs):
key = (args, tuple(sorted(kwargs.items())))
if key not in cache:
cache[key] = func(*args, **kwargs)
return cache[key]
return wrapper
@memoize
def expensiv…How to Create a Generator Context Manager in Python with contextlib
Create a custom context manager with the @contextlib.contextmanager decorator to manage resources using a generator function.
import contextlib
@contextlib.contextmanager
def temporary_directory():
"""Yield a string and clean up after the block exits."""
print("Creating temp directory...")
dir_name = "/tmp/example"
try:
yield dir_name
finally:
print(f"Removing {dir_name}...")
if __name__ == "__main__":
…How to implement exponential backoff for LLM API calls in Python
A decorator that retries flaky LLM API calls with exponential delay, using a mock client to demonstrate the pattern.
import time
import random
class MockLLM:
def call(self, prompt):
if random.random() < 0.7: # 70% chance of transient failure
raise ConnectionError("API unavailable")
return f"LLM response for: {prompt}"
def with_exponential_backoff(max_retries=5, base_delay=0.1):
def decorator(fu…How to Build a Sidecar Logging Proxy in Python
Wrap any object with a proxy that transparently logs every method call, arguments, return value, and execution time to a file — mimicking a sidecar pattern.
import logging
import time
from datetime import datetime
class LoggingProxy:
"""Sidecar-style proxy that logs all calls to a wrapped object."""
def __init__(self, target, log_file="proxy.log"):
self._target = target
logging.basicConfig(
filename=log_file,
level=loggin…How to Add TTL Jitter to Cache Expiration in Python
A Python decorator that adds random jitter to cache TTLs, staggering expiration times to prevent cache avalanche.
import random
import time
from functools import wraps
def add_jitter(ttl: float, jitter_range: float = 0.1) -> float:
"""Add random jitter (as % of TTL) to stagger cache expiration and prevent avalanche."""
jitter = random.uniform(-jitter_range, jitter_range)
return ttl * (1 + jitter)
def cache_with_jitt…How to Cache Function Results in Redis with Python
A Python decorator that caches function results in Redis using TTL, with optional fakeredis for testing without a server.
import redis
import json
import time
try:
import fakeredis
except ImportError:
fakeredis = None
from functools import wraps
def cache_redis(cache_key_prefix="cache", ttl=60):
"""Decorator to cache function results in Redis."""
if fakeredis:
r = fakeredis.FakeStrictRedis()
else:
r…How to Cap Retry Attempts in Python with a Decorator
Build a reusable retry decorator that caps attempts, adds delays, and lets flaky services fail fast instead of hanging.
import random
from functools import wraps
from time import sleep
def retry(max_attempts, delay=0.1):
def decorator(func):
@wraps(func)
def wrapper(*args, **kwargs):
attempts = 0
while attempts < max_attempts:
try:
return func(*args, **kw…Retry with Exponential Backoff and Jitter in Python
A decorator-style retry wrapper that retries a flaky function with exponential backoff plus random jitter, then raises after the last attempt fails.
import random
import time
def retry_with_backoff(func, max_retries=3, base_delay=0.5, max_jitter=0.1):
for attempt in range(max_retries + 1):
try:
return func()
except Exception as e:
if attempt == max_retries:
raise
delay = base_delay * (2 ** at…Lazy Evaluation Transform Lineage Mock in Python
Build a mock lineage tracker for data transforms using lazy evaluation and function wrappers in Python.
import functools
def lazy_transform(pipeline):
"""Build a mock lineage tracker using lazy evaluation."""
lineage = []
def wrap(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
result = func(*args, **kwargs)
lineage.append({"transform": func.__name__, "a…How to Mock a CORS Allow Origin Whitelist in Python
A decorator-based mock of a CORS middleware that whitelists allowed origins and injects proper Access-Control-Allow-Origin headers while rejecting others.
from functools import wraps
class MockCORSConfig:
def __init__(self, allowed_origins):
self.allowed_origins = allowed_origins
def is_origin_allowed(self, origin):
return origin in self.allowed_origins
def cors_middleware(config):
def decorator(handler):
@wraps(handler)
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