adding float attributes (#11)

Author: hallie

pynamodb_attributes/__init__.py

@@ -1,3 +1,4 @@
+from .float import FloatAttribute
 from .integer import IntegerAttribute
 from .integer_date import IntegerDateAttribute
 from .integer_enum import IntegerEnumAttribute
@@ -8,6 +9,7 @@
 from .unicode_enum import UnicodeEnumAttribute
 
 __all__ = [
+    'FloatAttribute',
     'IntegerAttribute',
     'IntegerDateAttribute',
     'IntegerEnumAttribute',

pynamodb_attributes/float.py

@@ -0,0 +1,11 @@
+from pynamodb.attributes import Attribute
+from pynamodb.attributes import NumberAttribute
+
+
+class FloatAttribute(Attribute):
+    """
+    Unlike NumberAttribute, this attribute has its type hinted as 'float'.
+    """
+    attr_type = NumberAttribute.attr_type
+    serialize = NumberAttribute.serialize
+    deserialize = NumberAttribute.deserialize

pynamodb_attributes/float.pyi

@@ -0,0 +1,5 @@
+from ._typing import Attribute
+
+
+class FloatAttribute(Attribute[float]):
+    ...

tests/float_attribute_test.py

@@ -0,0 +1,48 @@
+import pytest
+from pynamodb.attributes import UnicodeAttribute
+from pynamodb.models import Model
+
+from pynamodb_attributes import FloatAttribute
+from tests.meta import dynamodb_table_meta
+
+
+class MyModel(Model):
+    Meta = dynamodb_table_meta(__name__)
+
+    key = UnicodeAttribute(hash_key=True)
+    value = FloatAttribute(null=True)
+
+
+@pytest.fixture(scope='module', autouse=True)
+def create_table():
+    MyModel.create_table()
+
+
+def test_serialization_non_null(uuid_key):
+    model = MyModel()
+    model.key = uuid_key
+    model.value = 45.6
+    model.save()
+
+    # verify underlying storage
+    item = MyModel._get_connection().get_item(uuid_key)
+    assert item['Item']['value'] == {'N': '45.6'}
+
+    # verify deserialization
+    model = MyModel.get(uuid_key)
+    assert model.value == 45.6
+
+
+def test_serialization_null(uuid_key):
+    model = MyModel()
+    model.key = uuid_key
+    model.value = None
+    model.save()
+
+    # verify underlying storage
+    item = MyModel._get_connection().get_item(uuid_key)
+    assert 'value' not in item['Item']
+
+    # verify deserialization
+    model = MyModel.get(uuid_key)
+    assert model.value is None