add traits numpy file

Author: jasongrout

pythreejs/traits_numpy.py

@@ -0,0 +1,36 @@
+"""
+Simple serialization for numpy arrays
+"""
+
+import numpy as np
+from traitlets import Instance, TraitError, TraitType, Undefined
+
+# Format:
+# {'dtype': string, 'shape': tuple, 'array': memoryview}
+
+def array_to_json(value, widget):
+    return {
+        'shape': value.shape,
+        'dtype': str(value.dtype),
+        'buffer': memoryview(value) # maybe should do array.tobytes(order='C') to copy
+    }
+
+def array_from_json(value, widget):
+    # may need to copy the array if the underlying buffer is readonly
+    n = np.frombuffer(value['buffer'], dtype=value['dtype'])
+    n.shape = value['shape']
+    return n
+
+array_serialization = dict(to_json=array_to_json, from_json=array_from_json)
+
+def shape_constraints(*args):
+    """Example: shape_constraints(None,3) insists that the shape looks like (*,3)"""
+    def validator(trait, value):
+        if len(value.shape) != len(args):
+            raise TraitError('%s shape expected to have %s components, but got %s components'%(trait.name, len(args), (value, type(value))))
+        for i, constraint in enumerate(args):
+            if constraint is not None:
+                if value.shape[i] != constraint:
+                    raise TraitError('Dimension %i is supposed to be size %d, but got dimension %d'%(i, constraint, value.shape[i]))
+        return value
+    return validator