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Bulletproof json.dump?

On 2020-07-06 2:06 PM, Jon Ribbens via Python-list wrote:
> On 2020-07-06, Chris Angelico <rosuav at> wrote:
>> On Mon, Jul 6, 2020 at 8:36 PM Adam Funk <a24061 at> wrote:
>>> Is there a "bulletproof" version of json.dump somewhere that will
>>> convert bytes to str, any other iterables to list, etc., so you can
>>> just get your data into a file & keep working?
>> That's the PHP definition of "bulletproof" - whatever happens, no
>> matter how bad, just keep right on going.
> While I agree entirely with your point, there is however perhaps room
> for a bit more helpfulness from the json module. There is no sensible
> reason I can think of that it refuses to serialize sets, for example.
> Going a bit further and, for example, automatically calling isoformat()
> on date/time/datetime objects would perhaps be a bit more controversial,
> but would frequently be useful, and there's no obvious downside that
> occurs to me.

I may be missing something, but that would cause a downside for me.

I store Python lists and dicts in a database by calling dumps() when 
saving them to the database and loads() when retrieving them.

If a date was 'dumped' using isoformat(), then on retrieval I would not 
know whether it was originally a string, which must remain as is, or was 
originally a date object, which must be converted back to a date object.

There is no perfect answer, but my solution works fairly well. When 
dumping, I use 'default=repr'. This means that dates get dumped as 
', 7, 6)'. I look for that pattern on retrieval to 
detect that it is actually a date object.

I use the same trick for Decimal objects.

Maybe the OP could do something similar.

Frank Millman