Remove support for encoding audio without numpy for performance

IPython/lib/display.py

@@ -97,7 +97,6 b' class Audio(DisplayObject):'
         else:
             self.mimetype = "audio/wav"
             
-            
     def _make_wav(self,data,rate):
         """ Transform a numpy array to a PCM bytestring """
         import struct
@@ -105,13 +104,13 b' class Audio(DisplayObject):'
         import wave
         try:
             import numpy as np
+            data = np.array(data,dtype=float)
             if len(data.shape) > 1:
                 raise ValueError("encoding of stereo PCM signals are unsupported")
-            data = np.array(data,dtype=float)
-            scaled = list(np.int16(data/np.max(np.abs(data))*32767))
+            scaled = np.int16(data/np.max(np.abs(data))*32767).tolist()
         except ImportError:
-            maxabsvalue = float(max(map(abs,data)))
-            scaled = map(lambda x: int(x/maxabsvalue*32767), data)
+            print("Numpy is required to encode PCM from an array")
+            raise
         fp = BytesIO()
         waveobj = wave.open(fp,mode='wb')
         waveobj.setnchannels(1)