[odml/dtypes] Raise ValueError in tuple_get

Closes #354

Also updates the corresponding test.

Author: mpsonntag

odml/dtypes.py

@@ -328,12 +328,18 @@ def tuple_get(string, count=None):
     """
     if not string:
         return None
+
     string = string.strip()
-    assert string.startswith("(") and string.endswith(")")
+    if not (string.startswith("(") and string.endswith(")")):
+        msg = "Tuple value misses brackets: '%s'" % string
+        raise ValueError(msg)
+
     string = string[1:-1]
     res = [x.strip() for x in string.split(";")]
-    if count is not None:  # be strict
-        assert len(res) == count
+    if count is not None and not len(res) == count:
+        msg = "%s-tuple value does not match required item length" % count
+        raise ValueError(msg)
+
     return res
 
 

test/test_dtypes.py

@@ -213,10 +213,10 @@ def test_tuple(self):
         self.assertEqual(typ.tuple_get("(39.12; 67.19)"), ["39.12", "67.19"])
 
         # Test fail on missing parenthesis.
-        with self.assertRaises(AssertionError):
+        with self.assertRaises(ValueError):
             _ = typ.tuple_get("fail")
         # Test fail on mismatching element count and count number.
-        with self.assertRaises(AssertionError):
+        with self.assertRaises(ValueError):
             _ = typ.tuple_get("(1; 2; 3)", 2)
 
     def test_dtype_none(self):