Refactor node_cast_value to use large if/elif instead of dict lookup

mpv.py

@@ -196,18 +196,31 @@ def node_value(self, decoder=identity_decoder):
 
     @staticmethod
     def node_cast_value(v, fmt=MpvFormat.NODE, decoder=identity_decoder):
-        return {
-            MpvFormat.NONE:         lambda v: None,
-            MpvFormat.STRING:       lambda v: decoder(v.string),
-            MpvFormat.OSD_STRING:   lambda v: v.string.decode('utf-8'),
-            MpvFormat.FLAG:         lambda v: bool(v.flag),
-            MpvFormat.INT64:        lambda v: v.int64,
-            MpvFormat.DOUBLE:       lambda v: v.double,
-            MpvFormat.NODE:         lambda v: v.node.contents.node_value(decoder) if v.node else None,
-            MpvFormat.NODE_ARRAY:   lambda v: v.list.contents.array_value(decoder) if v.list else None,
-            MpvFormat.NODE_MAP:     lambda v: v.map.contents.dict_value(decoder) if v.map else None,
-            MpvFormat.BYTE_ARRAY:   lambda v: v.byte_array.contents.bytes_value() if v.byte_array else None,
-            }[fmt](v)
+        if fmt == MpvFormat.NONE:
+            return None
+        elif fmt == MpvFormat.STRING:
+            return decoder(v.string)
+        elif fmt == MpvFormat.OSD_STRING:
+            return v.string.decode('utf-8')
+        elif fmt == MpvFormat.FLAG:
+            return bool(v.flag)
+        elif fmt == MpvFormat.INT64:
+            return v.int64
+        elif fmt == MpvFormat.DOUBLE:
+            return v.double
+        else:
+            if not v.node: # Check for null pointer
+                return None
+            if fmt == MpvFormat.NODE:
+                return v.node.contents.node_value(decoder)
+            elif fmt == MpvFormat.NODE_ARRAY:
+                return v.list.contents.array_value(decoder)
+            elif fmt == MpvFormat.NODE_MAP:
+                return v.map.contents.dict_value(decoder)
+            elif fmt == MpvFormat.BYTE_ARRAY:
+                return v.byte_array.contents.bytes_value()
+            else:
+                raise TypeError('Unknown MPV node format {}. Please submit a bug report.'.format(fmt))
 
 class MpvNodeUnion(Union):
     _fields_ = [('string', c_char_p),