Python trio, Saving JSON under loop within

Question

Currently, am receiving a dict within my rec function coming from the receiver channel.

async def rec(receiver):
    with open('data.json', 'w', encoding='utf-8', buffering=1) as f:
        f.write('[\n')
        async with receiver:
            count = 0
            async for val in receiver:
                count += 1
                if count != 1:
                    f.write(',')
                json.dump(val, f, indent=4, ensure_ascii=False)
        print(f'[*] - Active items: {count}')
        f.write('\n]')

am not sure if that's count as the correct way to dump JSON into a file under a for loop! Please advise if there's more Pythonic way for that.

Well, you should probably check `if count:` *before* incrementing the count, instead of the `!= 1` test, but otherwise … not really; there's no comprehensive streaming JSON writer module out there AFAIK. — Matthias Urlichs, Dec 09 '22 at 16:51
@MatthiasUrlichs Thanks Matthias, can you please show me what you mean by `if count` ? — αԋɱҽԃ αмєяιcαη, Dec 09 '22 at 17:01
As comments don't lend themselves to multiline code fragments, I added an answer. — Matthias Urlichs, Dec 09 '22 at 17:17

score 1 · Accepted Answer · answered Dec 09 '22 at 17:16

Well, one improvement to make this code somewhat-more-pythonically-correct is to re-order the if count … test thus:

    async with receiver:
        count = 0
        async for val in receiver:
            if count:
                f.write(',')
            count += 1
            json.dump(val, f, indent=4, ensure_ascii=False)

Also, you might want to pass the file name in as a parameter, and add a linefeed after the comma.

As there's no non-trivial JSON streamer module out there AFAIK, I'd write this code mostly the same way.

Python trio, Saving JSON under loop within

1 Answers1