Somewhat unsatisfying/halfway solution to an issue with initializing …

…a frequency band with hz instances. Ideally, no raw floats or ints are ever used to represent hz, the same way time is represented wiht a semantically meaningful type

zounds/spectral/frequencyscale.py

@@ -5,17 +5,26 @@
 
 class Hertz(float):
     def __init__(self, hz):
-        self.hz = hz
+        try:
+            self.hz = hz.hz
+        except AttributeError:
+            self.hz = hz
 
     def __neg__(self):
         return Hertz(-self.hz)
 
     def __add__(self, other):
-        return Hertz(self.hz + other.hz)
+        try:
+            other = other.hz
+        except AttributeError:
+            pass
+        return Hertz(self.hz + other)
+
+    def __float__(self):
+        return self.hz
+
 
-
-class Hz(Hertz):
-    pass
+Hz = Hertz
 
 
 # TODO: What commonalities can be factored out of this class and TimeSlice?

zounds/spectral/test_frequencyscale.py

@@ -21,6 +21,13 @@ def test_can_subtract_hertz(self):
 
 
 class FrequencyBandTests(unittest2.TestCase):
+
+    def test_can_create_frequency_band_with_hertz_instances(self):
+        fb = FrequencyBand(Hz(20), Hz(20000))
+        self.assertIsInstance(fb.center_frequency, float)
+        self.assertEqual(20, fb.start_hz)
+        self.assertEqual(20000, fb.stop_hz)
+
     def test_can_create_from_center_frequency(self):
         fb = FrequencyBand.from_center(1000, 50)
         self.assertEqual(FrequencyBand(975, 1025), fb)