workaround for python json <= 2.7 datetime serializer not working

Question

This is a little bit complicated but I try to explain as best as I can. I have a class called Event with two attributes:

self.timestamp= datetime.now()
self.data = this is a big dictionary

I put all the instances of this class into a list and finally use json.dumps() to print the whole list to a file. json.dumps(self.timeline, indent=4, default=json_handler) I am using a python environment where I can install/modify libraries and I only have access to python json <= 2.7.

This is my workaround to handle datetime:

# workaround for python json <= 2.7 datetime serializer
def json_handler(obj):
    if hasattr(obj, 'isoformat'):
        return obj.isoformat()
    elif isinstance(obj, event.Event):
        return {obj.__class__.__name__ : obj.data}
    else:
        raise TypeError("Unserializable object {} of type {}".format(obj, type(obj)))

and everything seemed to work fine until I noticed that json does not print any timestamp. Why is that? what is happening?

Tommi Komulainen · Accepted Answer · 2013-05-27 19:53:31Z

1

When the serializer encounters your event.Event type you're only serializing its data attribute skipping the timestamp completely. You need to return the timestamp as well somehow. Maybe something like:

def json_handler(obj):
    if hasattr(obj, 'isoformat'):
        return obj.isoformat()
    elif isinstance(obj, Event):
        attrs = dict(data=obj.data, timestamp=obj.timestamp)
        return {obj.__class__.__name__: attrs}
    else:
        raise TypeError("Unserializable object {} of type {}".format(obj, type(obj)))

answered May 27, 2013 at 19:53

Tommi Komulainen

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1 Comment

theAlse Over a year ago

Thank you! I knew that I had to return the time-stamps as well but I did not know how to do it only. I will test this and let you know as well!

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