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I'm wondering how to serialize a dict of nested Schema.
Naively, I would expect syntaxes like this to work:
fields.List(Schema)
fields.Dict(Schema)
or maybe
fields.List(fields.Nested(Schema))
fields.Dict(fields.Nested(Schema))
Serializing a list of Schema can be achieved through Nested(Schema, many=True), but I don't know about a dict of Schema.
Assume, for example's sake, that my object is defined like this:
from marshmallow import Schema, fields, pprint
class AlbumSchema(Schema):
year = fields.Int()
class ArtistSchema(Schema):
name = fields.Str()
# What should I write, here?
# This won't work
albums = fields.Nested(AlbumSchema(), many=True)
# If I write this, AlbumSchema is ignored, so this is equivalent to
albums = fields.Dict(AlbumSchema(), many=True)
# this, which is not satisfying (AlbumSchema unused)
albums = fields.Dict()
# This is not the way either
albums = fields.Dict(fields.Nested(AlbumSchema))
album_1 = dict(year=1971)
album_2 = dict(year=1970)
bowie = dict(name='David Bowie',
albums={
'Hunky Dory': album_1,
'The Man Who Sold the World': album_2
}
)
schema = ArtistSchema()
result = schema.dump(bowie)
pprint(result.data, indent=2)
I expect my object to be serialized as
{ 'albums': { 'Hunky Dory': {'year': 1971},
'The Man Who Sold the World': {'year': 1970}},
'name': 'David Bowie'}
(Question also discussed on GitHub.)
977
Schemas can be nested to represent relationships between objects (e.g. foreign key relationships). For example, a Blog may have an author represented by a User object. import datetime as dt class User: def __init__(self, name, email): self.
In short, marshmallow schemas can be used to: Validate input data. Deserialize input data to app-level objects. Serialize app-level objects to primitive Python types. The serialized objects can then be rendered to standard formats such as JSON for use in an HTTP API.
This is not possible right now, but it is a feature request:
and it has been worked on already:
2017-12-31: This feature was added to Marshmallow 3.0.0b5 (https://github.com/marshmallow-code/marshmallow/pull/700).
190
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