Implement JSON serialization for numpy dtypes (#2456)

Fixes #2453

cirq/protocols/json.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import json
+import numbers
 import pathlib
 from typing import (
     Union,
@@ -230,7 +231,13 @@ class CirqEncoder(json.JSONEncoder):
     def default(self, o):
         if hasattr(o, '_json_dict_'):
             return o._json_dict_()
-        if isinstance(o, complex):
+        if isinstance(o, np.bool_):
+            return bool(o)
+        if isinstance(o, numbers.Integral):
+            return int(o)
+        if isinstance(o, numbers.Real):
+            return float(o)
+        if isinstance(o, numbers.Complex):
             return {
                 'cirq_type': 'complex',
                 'real': o.real,

cirq/protocols/json_test.py

@@ -528,13 +528,34 @@ def _roundtrip_test_classes() -> Iterator[Tuple[str, Type]]:
 
 
 def test_builtins():
+    assert_roundtrip(True)
+    assert_roundtrip(1)
     assert_roundtrip(1 + 2j)
     assert_roundtrip({
         'test': [123, 5.5],
         'key2': 'asdf',
         '3': None,
         '0.0': [],
     })
+
+
+def test_numpy():
+    x = np.ones(1)[0]
+
+    assert_roundtrip(x.astype(np.bool))
+    assert_roundtrip(x.astype(np.int8))
+    assert_roundtrip(x.astype(np.int16))
+    assert_roundtrip(x.astype(np.int32))
+    assert_roundtrip(x.astype(np.int64))
+    assert_roundtrip(x.astype(np.uint8))
+    assert_roundtrip(x.astype(np.uint16))
+    assert_roundtrip(x.astype(np.uint32))
+    assert_roundtrip(x.astype(np.uint64))
+    assert_roundtrip(x.astype(np.float32))
+    assert_roundtrip(x.astype(np.float64))
+    assert_roundtrip(x.astype(np.complex64))
+    assert_roundtrip(x.astype(np.complex128))
+
     assert_roundtrip(np.ones((11, 5)))
     assert_roundtrip(np.arange(3))