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How to Monitor USB Device Connections in Python
A Python utility that monitors USB device connections and disconnections by comparing output of the lsusb command at regular intervals.
import time
import subprocess
import os
def get_usb_devices():
"""Return list of currently connected USB devices (Linux)."""
try:
result = subprocess.run(['lsusb'], capture_output=True, text=True, check=True)
return result.stdout.strip().split('\n')
except (subprocess.CalledProcessError, F…How to Sync Two Directories in Python (rsync-like)
Mirror a source directory into a destination by copying new or changed files and deleting extras, similar to rsync.
import os
import shutil
import sys
from pathlib import Path
def sync_dirs(src: Path, dst: Path):
"""Mirror src into dst: copy new files, overwrite changed, delete extras."""
dst.mkdir(parents=True, exist_ok=True)
for dst_entry in dst.rglob('*'):
rel = dst_entry.relative_to(dst)
src_entry =…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…Python: Archive Old Logs by Compressing Gzip by Age
A Python script that finds .log files older than a specified age and compresses them into .gz archives while removing the originals.
import gzip
import os
import shutil
from pathlib import Path
def archive_logs(log_dir: str, max_age_days: int) -> list[str]:
"""Compress log files older than max_age_days into .gz archives.
Returns a list of compressed file paths.
"""
cutoff = time.time() - max_age_days * 86400
compressed = …Track Internet Connectivity and Downtime Automatically in Python
Monitors internet connectivity by pinging a remote host and logs any downtime events with timestamps and duration.
import time
import subprocess
from datetime import datetime
def check_internet(host="8.8.8.8", timeout=3):
"""Returns True if internet is reachable via ping."""
try:
subprocess.run(
["ping", "-c", "1", "-W", str(timeout), host],
capture_output=True,
timeout=timeout …How to Count Events by Minute with a Tumbling Window in Python
Group timestamps into fixed 60-second tumbling windows and count events per bucket using a dict.
from collections import defaultdict
from datetime import datetime, timedelta
def tumbling_window_count(events, window_seconds=60):
buckets = defaultdict(int)
for event in events:
ts = datetime.fromisoformat(event["timestamp"])
bucket_start = ts - timedelta(seconds=ts.second % window_seconds,
…How to Stream a Large JSONL File Line by Line in Python
Process a large JSON-lines file incrementally using streaming techniques to avoid loading the entire file into memory.
import json
def process_large_file(filepath, chunk_size=8192):
"""
Stream a large JSON-lines file line by line, processing each record
without loading the entire file into memory.
"""
total_count = 0
total_sum = 0
with open(filepath, 'r') as f:
while True:
chunk = …Python Exponential Backoff Retry Example
Retry a flaky function with exponential backoff and jitter-free delays, printing each attempt and finally returning the successful result.
import random
import time
def flaky_function():
if random.random() < 0.6:
raise ConnectionError("Temporary network error")
return "success"
def retry_with_exponential_backoff(func, max_retries=5, base_delay=1.0):
for attempt in range(max_retries + 1):
try:
return func()
…Find the Commit That Introduced a String in Git History Using Python
Use git log -S with Python subprocess to find the earliest commit that introduced a specific string across your repository history.
import subprocess
import sys
def find_introducing_commit(repo_path: str, search_string: str, file_glob: str = "*") -> str:
"""Find the first commit that introduced a given string in a git repository."""
result = subprocess.run(
["git", "-C", repo_path, "log", "--all", "--oneline", "-S", search_string…How to Generate Release Notes from Git Commit Messages in Python
This script fetches recent Git commit messages using conventional commit prefixes (feat, fix, etc.), categorizes them, and prints formatted release notes with today's date.
import subprocess
import re
from datetime import datetime
def get_git_log(since_tag="HEAD~10", format_str="%s"):
"""Retrieve commit messages from git log."""
try:
result = subprocess.run(
["git", "log", f"--since={since_tag}", f"--format={format_str}"],
capture_output=True,
…How to Make a Git Commit Heatmap by Hour in Python
Parse a git log output and count commits by weekday and hour, then print a compact heatmap table.
import re
from collections import Counter
from datetime import datetime
def parse_commits(log_text):
"""Parse git log lines and count commits by (weekday, hour)."""
pattern = re.compile(r"^Date:\s+(.+)$")
counts = Counter()
for line in log_text.splitlines():
match = pattern.match(line)
…How to generate and parse an interactive rebase TODO list in Python
Generate a Git interactive rebase TODO list from commit data and parse it back into structured records.
import re
from collections import namedtuple
Commit = namedtuple("Commit", ["hash", "subject"])
def generate_rebase_todo(commits, action="pick"):
todo_lines = []
for i, commit in enumerate(commits):
if i == 0 and action == "reword":
todo_lines.append(f"reword {commit.hash} {commit.subject…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…Mock S3, GCS, and Azure storage with a Python abstract interface
Define an abstract Storage interface and implement a local, filesystem-backed mock so S3, GCS, and Azure code can be tested without cloud dependencies.
from abc import ABC, abstractmethod
from pathlib import Path
class Storage(ABC):
@abstractmethod
def put(self, name: str, data: bytes) -> None:
pass
@abstractmethod
def get(self, name: str) -> bytes:
pass
class LocalStorage(Storage):
def __init__(self, base_dir: str = "mock_sto…How to Mock a PEP 517 Build Backend in Python
Use unittest.mock.Mock to simulate a PEP 517 backend interface, stub build hooks, and verify calls for package build automation.
import json
from unittest.mock import Mock
# Simulate a PEP 517 backend interface
class Pep517Backend:
def build_wheel(self, wheel_directory, config_settings=None, metadata_directory=None):
return f"{wheel_directory}/mock_package-1.0.0-py3-none-any.whl"
def get_requires_for_build_wheel(self, config_s…How to Mock a semantic-release Changelog in Python
This Python code simulates a semantic-release changelog generator, grouping commits by type and formatting them into a markdown changelog.
import json
from datetime import datetime
class SemanticReleaseChangelog:
def __init__(self, version, commits):
self.version = version
self.commits = commits
self.release_date = datetime.now().isoformat()
def generate_changelog(self):
grouped = {}
for commit in self.c…How to set up mypy strict mode in Python
Demonstrates how to configure and run mypy in strict mode to enforce full type annotation coverage across a Python project.
from typing import Dict, Optional
def describe_user(name: str, age: int, email: Optional[str] = None) -> Dict[str, object]:
"""Build a user description dictionary with strict type annotations."""
user: Dict[str, object] = {"name": name, "age": age}
if email is not None:
user["email"] = email
…Build a Python Performance Profiler That Generates Readable Reports
Use cProfile and pstats to profile Python functions and print a sorted performance report showing the top time-consuming calls.
import cProfile
import pstats
import io
from pathlib import Path
def slow_function():
total = 0
for i in range(500_000):
total += i ** 2
return total
def fast_function():
total = sum(i * i for i in range(500_000))
return total
def profile_functions():
profiler = cProfile.Profile()
…How to Implement a Batch Requests Flush Interval in Python
A simple async batcher that accumulates items and flushes them either when a max batch size is reached or after a time-based flush interval.
import asyncio
from collections import deque
class Batcher:
def __init__(self, flush_interval=0.5, max_batch=5):
self.flush_interval = flush_interval
self.max_batch = max_batch
self.queue = deque()
self.lock = asyncio.Lock()
async def add(self, item):
async with self.l…How to Profile CPU Hot Path in Python with cProfile and sort_stats cumtime
Profile a Python function's CPU usage by running cProfile, sorting stats by cumulative time, and printing a readable report to stdout.
import cProfile
import pstats
import io
def slow_function():
total = 0
for i in range(100_000):
total += i * i
return total
def fast_function():
return sum(i for i in range(100))
def main():
slow_function()
fast_function()
if __name__ == "__main__":
profiler = cProfile.Profi…How to Share a Queue Between Processes in Python
Use multiprocessing.Queue to pass work from a producer process to multiple consumer processes, coordinating with a sentinel stop message.
import multiprocessing
import time
def producer(queue, items):
for item in items:
queue.put(item)
time.sleep(0.1)
queue.put("STOP")
def consumer(queue, name):
while True:
item = queue.get()
if item == "STOP":
break
print(f"{name} processed: {item}")
…Merge K Sorted Lists in Python with heapq
Merge k sorted lists into one sorted list in O(N log k) time using a min-heap of current elements.
import heapq
def merge_k_sorted_lists(lists):
heap = []
for i, lst in enumerate(lists):
if lst: # only push non-empty lists
heapq.heappush(heap, (lst[0], i, 0))
result = []
while heap:
val, list_idx, elem_idx = heapq.heappop(heap)
result.append(val)
if elem…Profile Memory Usage with tracemalloc Snapshot Diff in Python
Use tracemalloc to take two memory snapshots, compute a diff, and print the top changes (size and count) by line number.
import tracemalloc
def profile_memory():
tracemalloc.start()
# Allocate some objects to track
data = [i * 2 for i in range(10000)]
text = "x" * 5000
nested = {"key": [1, 2, 3], "value": (4, 5)}
# Take first snapshot
snapshot1 = tracemalloc.take_snapshot()
# Free some mem…How to Load Test a Local API with Locust in Python
Defines a Locust load test that simulates traffic to local endpoints, enabling manual load testing against a development server.
from locust import HttpUser, task, between
class WebsiteUser(HttpUser):
wait_time = between(1, 3)
@task
def home_page(self):
self.client.get("/")
@task(3)
def about_page(self):
self.client.get("/about")
if __name__ == "__main__":
print("Run with: locust -f this_file.py --h…Browse by section
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How to use this library
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- Open a sample, read How it works, and copy the code block
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Samples vs tutorials and challenges
Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.