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Concurrency & performance

asyncio, threading, multiprocessing, and profiling-friendly performance patterns.

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Concurrency & performance medium

Limit Concurrency with asyncio.Semaphore in Python

Use asyncio.Semaphore to cap how many async tasks run at once, throttling a batch of coroutines to a set concurrency limit.

asyncio concurrency semaphore
Python 
import asyncio
import random


async def fetch_data(i: int, semaphore: asyncio.Semaphore) -> str:
    async with semaphore:
        print(f"Task {i} starts")
        await asyncio.sleep(random.uniform(0.1, 0.5))
        print(f"Task {i} finishes")
        return f"Result {i}"


async def main() -> None:
    semaphore …
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