Short way to serialize datetime with marshmallow

Question

Here is my situation: I store some datetime in MSSQL, which i get in my python application via SQLAlchemy, and then serialize it thru Marshmallow like this:

class MyVisitSchema(Schema):
    cafe = fields.Nested(CafeSchema)
    started_at = fields.DateTime()
    ended_at = fields.DateTime()

    class Meta:
        additional = ('duration',)
        ordered = True

But here the problem: after serialization i get something like "started_at": "1994-05-20T00:00:00+00:00" which says that UTC+0, but i store all my dates in DB without any timezone info, but in UTC+3.

I know that i can use fields.Method() to change output timezone, but it looks inconvenient. Any ideas how to make my serializer work as it should?)

score 16 · Accepted Answer · answered Mar 04 '16 at 13:04

16

Found some info in official documentaries. So, my issue can be solved using

started_at = fields.DateTime('%Y-%m-%dT%H:%M:%S+03:00')

hardcode a bit, but looks better than using additional function with fields.Method()

answered Mar 04 '16 at 13:04

Alexey Lysenko

1,890
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score 8 · Answer 2 · edited Apr 16 '19 at 10:25

8

If it does not work, use the keyword format

started_at = fields.DateTime(format='%Y-%m-%dT%H:%M:%S+03:00')

edited Apr 16 '19 at 10:25

Zoe

27,060
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answered Apr 16 '19 at 09:51

Michał Dobrzyński

106
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Waket Zheng · Answer 3 · 2019-06-12T09:19:55.970

5

I would rather use datetimeformat, see: https://marshmallow.readthedocs.io/en/3.0/api_reference.html

Example:

class MyVisitSchema(Schema):
    cafe = fields.Nested(CafeSchema)
    started_at = fields.DateTime()
    ended_at = fields.DateTime()

    class Meta:
        additional = ('duration',)
        ordered = True
        # dateformat = '%Y-%m-%dT%H:%M:%S%z'
        dateformat = '%Y-%m-%dT%H:%M:%S+03:00'

And I prefer to:

class BaseSchema(Schema):
    class Meta:
        dateformat = '%Y-%m-%dT%H:%M:%S+03:00'


class MyVisitSchema(BaseSchema):
    cafe = fields.Nested(CafeSchema)
    started_at = fields.DateTime()
    ended_at = fields.DateTime()

    class Meta(BaseSchema.Meta):
        additional = ('duration',)
        ordered = True

edited Jun 12 '19 at 09:19

answered May 29 '19 at 08:17

Waket Zheng

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I had to explicitly use the `DateTime(format='...')` syntax instead of the `Meta.dateformat` one for the release 3.0.0rc5. Did work before though. – cr0 May 31 '19 at 11:00
4

`Meta.dateformat` has been renamed to `Meta.datetimeformat`; see the [upgrade docs](https://marshmallow.readthedocs.io/en/latest/upgrading.html#datetime-field-dateformat-meta-option-is-renamed-datetimeformat) for reference. – GergelyPolonkai Aug 29 '19 at 07:43

Short way to serialize datetime with marshmallow

3 Answers3