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Easy snippets you can copy, study, and run in the browser editor.
How to Use threading.Lock to Synchronize a Counter in Python
Safely increment a shared counter across multiple threads using threading.Lock as a mutex to prevent race conditions.
import threading
counter = 0
lock = threading.Lock()
def increment():
global counter
for _ in range(100000):
with lock:
counter += 1
threads = [threading.Thread(target=increment) for _ in range(5)]
for t in threads:
t.start()
for t in threads:
t.join()
print(f"Final counter valu…Synchronize Threads with a Barrier in Python
Demonstrates using threading.Barrier to synchronize multiple threads at phase boundaries, ensuring all workers wait for each other before proceeding.
import threading
import time
from random import randint
def worker(barrier, worker_id):
for phase in range(3):
time.sleep(randint(1, 3))
print(f"Worker {worker_id} finished phase {phase} at {time.time():.2f}")
barrier.wait()
print(f"Worker {worker_id}: all phases complete")
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Guide: free Python code samples library
Copy-ready Python snippets for learners and developers
PythonSkillset code samples are short, focused examples organised by topic and difficulty. Every snippet is server-rendered HTML — readable by search engines and easy to copy. Open any sample, read the notes, copy the code, then press Try in editor to run it in the browser with Pyodide.
How to use this library
- Pick a topic section — strings, lists, files, functions, and more
- Open a sample, read How it works, and copy the code block
- Run it in the IDE, tweak values, then take a related quiz or tutorial lesson
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.