README.md

pynamodb-encoder

Introduction

pynamodb-encoder provides helper classes that can convert PynamoDB Model objects into JSON serializable dict. It can also decode such dict back into those Model objects. Polymorphic models and attributes are also supported.

Examples

def test_encode_complex_model(encoder: Encoder):
    class Pet(DynamicMapAttribute):
        cls = DiscriminatorAttribute()
        name = UnicodeAttribute()

    class Cat(Pet, discriminator="Cat"):
        pass

    class Dog(Pet, discriminator="Dog"):
        pass

    class Human(Model):
        name = UnicodeAttribute()
        pets = ListAttribute(of=Pet)

    jon = Human(name="Jon", pets=[Cat(name="Garfield", age=43), Dog(name="Odie")])
    assert encoder.encode(jon) == {
        "name": "Jon",
        "pets": [{"cls": "Cat", "name": "Garfield", "age": 43}, {"cls": "Dog", "name": "Odie"}],
    }

def test_decode_complex_model(decoder: Decoder):
    class Pet(DynamicMapAttribute):
        cls = DiscriminatorAttribute()

    class Cat(Pet, discriminator="Cat"):
        name = UnicodeAttribute()

    class Dog(Pet, discriminator="Dog"):
        breed = UnicodeAttribute()

    class Human(Model):
        name = UnicodeAttribute()
        age = NumberAttribute()
        pets = ListAttribute(of=Pet)

    jon = decoder.decode(
        Human,
        {
            "name": "Jon",
            "age": 70,
            "pets": [{"cls": "Cat", "name": "Garfield"}, {"cls": "Dog", "breed": "Terrier"}],
        },
    )

    assert jon.name == "Jon"
    assert jon.age == 70
    assert isinstance(jon.pets, list)
    assert len(jon.pets) == 2
    assert isinstance(jon.pets[0], Cat)
    assert jon.pets[0].name == "Garfield"
    assert isinstance(jon.pets[1], Dog)
    assert jon.pets[1].breed == "Terrier"

More examples can be found in encoder_test.py and decoder_test.py