demo_source_auto_samplerate.py: add example of automatic samplerate selection

diff --git a/python/demos/demo_source_auto_samplerate.py b/python/demos/demo_source_auto_samplerate.py
new file mode 100755 (executable)
index 0000000..31ba55a
--- /dev/null
+++ b/python/demos/demo_source_auto_samplerate.py
@@ -0,0 +1,17 @@
+#! /usr/bin/env python
+
+import sys
+from aubio import source
+
+if __name__ == '__main__':
+  if len(sys.argv) < 2:
+    print 'usage: %s <inputfile>' % sys.argv[0]
+    sys.exit(1)
+  f = source(sys.argv[1], 0, 256)
+  samplerate = f.get_samplerate()
+  total_frames, read = 0, 256
+  while read:
+    vec, read = f()
+    total_frames += read
+  print f.uri, "is",
+  print "%.2f seconds long at %.1fkHz" % (total_frames / float(samplerate), samplerate / 1000. )