Python Snippets

Asynchronous File Downloader with Progress Bar

This snippet demonstrates how to download files asynchronously in Python while displaying a progress bar. It uses aiohttp for asynchronous HTTP requests and tqdm for the progress bar visualization.

import aiohttp
import asyncio
from tqdm import tqdm

async def download_file(url, destination):
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as response:
            if response.status != 200:
                raise Exception(f"Failed to download file: HTTP {response.status}")
            
            total_size = int(response.headers.get('content-length', 0))
            block_size = 1024  # 1 KB
            
            with open(destination, 'wb') as file, tqdm(
                total=total_size,
                unit='B',
                unit_scale=True,
                desc=f"Downloading {destination}"
            ) as progress_bar:
                async for chunk in response.content.iter_chunked(block_size):
                    file.write(chunk)
                    progress_bar.update(len(chunk))

async def main():
    url = "https://example.com/largefile.zip"
    destination = "largefile.zip"
    await download_file(url, destination)

if __name__ == "__main__":
    asyncio.run(main())

Explanation

What It Does

• The script downloads a file from a given URL asynchronously, making it efficient for large files or multiple downloads.
• It displays a progress bar using tqdm, showing the download progress in real-time.
• The file is saved to the specified destination path.

Why It’s Useful

• Efficiency: Uses aiohttp for non-blocking HTTP requests, improving performance.
• User Feedback: The progress bar (tqdm) provides visual feedback, which is helpful for large downloads.
• Error Handling: Checks HTTP status and raises an exception if the download fails.

How to Run

1. Install dependencies:

   pip install aiohttp tqdm
   

2. Replace url and destination in the main() function with your desired file and output path.
3. Run the script:

   python downloader.py
   

This snippet is ideal for scripts requiring efficient file downloads with a user-friendly progress indicator.