Add example Python script to list plugin presets

AUTHORS

@@ -8,4 +8,7 @@ Dynamic manifest support:
 	Stefano D'Angelo
 
 Plugin execution via Python bindings:
-    Kaspar Emanuel <kaspar.emanuel@gmail.com>
+    Kaspar Emanuel <kaspar.emanuel@gmail.com>
+
+Python preset script:
+    Christopher Arndt <chris@chrisarndt.de>

bindings/python/lv2_list_presets.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+import sys
+import lilv
+
+
+NS_PRESETS = "http://lv2plug.in/ns/ext/presets#"
+
+
+def print_presets(uri):
+    """Print all presets of an LV2 plugin to stdout."""
+
+    world = lilv.World()
+    world.load_all()
+    world.ns.presets = lilv.Namespace(world, NS_PRESETS)
+    plugins = world.get_all_plugins()
+    plugin = plugins[uri]
+    presets = plugin.get_related(world.ns.presets.Preset)
+
+    preset_list = []
+    for preset in presets:
+        world.load_resource(preset)
+        labels = world.find_nodes(preset, world.ns.rdfs.label, None)
+        label = str(labels[0]) if len(labels) > 0 else ""
+
+        if not label:
+            sys.stderr.write("warning: Preset <%s> has no label\n" % preset)
+
+        preset_list.append((str(preset), str(label)))
+
+    for preset in sorted(preset_list):
+        print('<%s> "%s"' % preset)
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 2:
+        sys.stderr.write("Usage: %s PLUGIN_URI\n" % (sys.argv[0]))
+        sys.exit(1)
+
+    try:
+        print_presets(sys.argv[1])
+    except ValueError as e:
+        sys.stderr.write("error: %s\n" % e)
+    except KeyError as e:
+        sys.stderr.write("error: %s\n" % str(e).strip("'"))