How can I log date and datetime as strings with structlog?

Question

Structlog seems to use __repr__ when creating log messages, which leads to date and datetime objects looking like 'datetime.datetime(2018, 9, 20, 10, 1, 52, 414750)' where '2018-09-20 10:01:52.414750' would be preferable.

I would have thought there would be an off the shelf processor to handle this, but I can't find one.

Answer 1

This is the solution I came up with, but I'm concerned about the performance given the highly recursive nature of it, and the unnecessary rebuilding of list and dict objects.

def _convert_dates(obj):
    if isinstance(obj, datetime.date):
        # all datetimes are also dates
        return str(obj)
    elif isinstance(obj, dict):
        # Assume dates won't be keys
        return {k: _convert_dates(v) for k, v in obj.items()}
    elif isinstance(obj, list):
        return [_convert_dates(v) for v in obj]
    return obj


def dates_to_str_filter(_, __, event):
    return _convert_dates(event)

Then include dates_to_str_filter in processors for the structlog.configure call.