implement a Field class similar to fields in Django, Marshmallow and DRF

carousel/core/__init__.py

@@ -277,3 +277,16 @@ def get_parents(bases, parent):
         :rtype: list
         """
         return [b for b in bases if isinstance(b, parent)]
+
+
+class Field(object):
+    _attrs = []
+
+    def __init__(self, *args, **kwargs):
+        for attr, val in zip(self._attrs, args):
+            setattr(self, attr, val)
+        for key, val in kwargs.iteritems():
+            if key in self._attrs:
+                setattr(self, key, val)
+            else:
+                LOGGER.warning('This key: "%s" is not an attribute.', key)

carousel/tests/test_core.py

@@ -2,7 +2,7 @@
 Test Carousel core.
 """
 
-from carousel.core import Q_, UREG
+from carousel.core import Q_, UREG, Field
 from nose.tools import eq_, ok_
 
 
@@ -15,3 +15,14 @@ def test_pv_context():
     esun = Q_(0.8765, UREG.suns)
     ok_(esun.dimensionless)
     eq_(esun.to('W / m ** 2', 'pv'), 876.5 * UREG.W / UREG.m / UREG.m)
+
+
+def test_fields():
+    """
+    Test that Carousel field creates an object with attributes
+    """
+    Field._attrs = ['units', 'isconstant']
+    test_field = Field('my test field', units='W/m**2', isconstant=True)
+    ok_(isinstance(test_field, Field))
+    eq_(getattr(test_field, 'units'), 'W/m**2')
+    return test_field

carousel/tests/test_fields.py

@@ -0,0 +1,30 @@
+"""
+Testing field subclasses in different layers.
+"""
+
+from carousel.core import Field, UREG
+from carousel.core.data_sources import DataSource
+from carousel.contrib.readers import ArgumentReader
+
+
+class VelocityData(DataSource):
+    data_reader = ArgumentReader
+    data_cache_enabled = False
+    Field._attrs = ['units', 'isconstant', 'uncertainty', 'argpos']
+    distance = Field(units='m', isconstant=True, uncertainty=0.01, argpos=0)
+    elapsed_time = Field(units='s', isconstant=True, uncertainty=0.01, argpos=1)
+
+    def __prepare_data__(self):
+        pass
+
+
+def test_data_with_fields():
+    v = VelocityData(distance=96540, elapsed_time=3600)
+    assert isinstance(v, DataSource)
+    assert v['distance'] == 96540 * UREG.m
+    assert v['distance'] == 3600 * UREG.s
+    return v
+
+
+if __name__ == '__main__':
+    v = test_data_with_fields()