Show that asyncio can be run on local files

asyncio-local.py

#!/usr/bin/env python3

import asyncio
from pathlib import Path

async def line_count(filename):
    try:
        count = filename.read_text(encoding='utf-8').count('\n')
    except:
        count = -1
    return (filename, count)

async def main():
    result = await asyncio.gather(
        *[line_count(p) for p in Path('.').glob('*.txt')]
    )
    for r in result:
        print(f"{str(r[0])} {r[1]}")
    
if __name__ == '__main__':
    asyncio.run(main())

But not actually run asynchronously, hahaha.

The file I/O is blocking, so it is not running asynchronously, notwithstanding that asyncio is running the code.

Try this to check async.

pip install aiofiles

#!/usr/bin/env python3

import asyncio
from pathlib import Path
import aiofiles

async def line_count(filename: Path):
    count = 0
    try:
        async with aiofiles.open(filename, mode='r', encoding='utf-8') as f:
            async for _ in f:
                count += 1
    except Exception:
        count = -1
    return (filename, count)

async def main():
    txt_files = list(Path('.').glob('*.txt'))
    result = await asyncio.gather(*(line_count(f) for f in txt_files))
    for file, count in result:
        print(f"{file} {count}")

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