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How to Write a Python Decorator with functools.wraps
Create a decorator that wraps a function while preserving its metadata using functools.wraps.
from functools import wraps
def logger(func):
@wraps(func)
def wrapper(*args, **kwargs):
print(f"Calling {func.__name__}")
return func(*args, **kwargs)
return wrapper
@logger
def greet(name):
"""Return a friendly greeting."""
return f"Hello, {name}!"
if __name__ == "__main__":…How to Sort Data in Python with a Class Helper
This beginner-friendly class wraps the built-in sorted() function to sort numbers, strings ignoring case, and dictionaries by a specified key.
class DataSorter:
def __init__(self, data):
self.data = data
def sort_numbers(self, reverse=False):
return sorted(self.data, reverse=reverse)
def sort_strings_ignore_case(self, reverse=False):
return sorted(self.data, key=str.lower, reverse=reverse)
def sort_dicts_by_key(self…Circuit Breaker Pattern in Python for LLM API Calls
Implements a circuit breaker class that wraps LLM client calls to fail fast when the service is degrading, then recover automatically after a timeout.
import time
class CircuitBreaker:
def __init__(self, failure_threshold=3, recovery_timeout=5):
self.failure_threshold = failure_threshold
self.recovery_timeout = recovery_timeout
self.failure_count = 0
self.state = "closed"
self.last_failure_time = None
def call(self, …How to Mock subprocess Calls in Python with unittest.mock
A Python script that wraps Vagrant up/destroy commands using subprocess, with tests that mock the subprocess call to simulate outputs and errors.
import subprocess
from unittest.mock import patch, Mock
def run_vagrant(action: str) -> str:
result = subprocess.run(
["vagrant", action],
capture_output=True,
text=True,
check=False,
)
return result.stdout.strip()
def vagrant_wrapper(action: str) -> str:
if action n…How to Build a Git Helper Class in Python
A beginner-friendly GitHelper class that wraps common git commands (status, log, branch) into reusable Python methods with structured output.
import subprocess
import json
from pathlib import Path
class GitHelper:
def __init__(self, repo_path="."):
self.repo = Path(repo_path)
def run(self, *args):
result = subprocess.run(
["git", *args],
cwd=self.repo,
capture_output=True,
text=True,…How to Mock a Metrics Decorator in Python with unittest.mock
This code demonstrates a timing decorator that wraps a function to measure execution time and prints the duration, with a unit test using unittest.mock to patch the print function and assert it was called.
import time
from functools import wraps
from unittest.mock import patch
def add_metrics(func):
@wraps(func)
def wrapper(*args, **kwargs):
start = time.perf_counter()
result = func(*args, **kwargs)
elapsed = time.perf_counter() - start
print(f"{func.__name__} took {elapsed:.6f}s…How to Wrap Message Attributes in a CloudEvent with Python
Create a minimal CloudEvent dataclass that wraps arbitrary message attributes into a JSON envelope, matching CloudEvents 1.0 spec.
import json
from dataclasses import dataclass, field, asdict
from typing import Any, Dict
from datetime import datetime, timezone
@dataclass
class CloudEvent:
message_attributes: Dict[str, Any] = field(default_factory=dict)
def wrap(self, event_id: str, source: str, event_type: str, data: Any):
self…How to Mock Cache Tag Invalidation in Python
Use unittest.mock.patch with wraps to verify tagged cache entries are invalidated correctly.
import unittest
from unittest.mock import patch
def get_cached_data(cache, key):
"""Return data from cache if present and valid, else None."""
if cache.get(key, {}).get("valid", False):
return cache[key]["data"]
return None
def invalidate_tag_mock(cache, tag):
"""Invalidate all cache entries …Mocking a Metrics Gauge's set_value Method in Python
Demonstrates using unittest.mock.Mock with wraps to intercept a gauge's set_value call while verifying arguments and preserving real behavior.
from unittest.mock import Mock
class MetricsGauge:
def __init__(self, name):
self.name = name
self.value = 0.0
def set_value(self, new_value):
self.value = float(new_value)
return self.value
# Usage demonstration with a mock
gauge = MetricsGauge("cpu_usage")
gauge_mock = Mock…Fallback cached response mock in Python
Wraps a mock function with a fallback to a real service and caches results to mask transient failures.
import time
from functools import wraps
class CachedMock:
def __init__(self, cache_ttl=5):
self.cache = {}
self.cache_ttl = cache_ttl
def get(self, key):
cached = self.cache.get(key)
if cached and time.time() - cached["timestamp"] < self.cache_ttl:
return cached["v…Browse by section
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