make sure stream names are unique, add get stream function

Hlt/Moore/python/Moore/streams.py

@@ -117,13 +117,21 @@ class Streams(object):
     """
 
     def __init__(self, streams):
-        self.streams = list(
-            filter(lambda stream: len(stream.lines) > 0,
-                   sorted(streams, key=lambda stream: stream.name)))
+        self.streams = self._streams(streams)
         self.lines = self._lines()
         self.physics_lines = self._physics_lines()
         self.lumi_lines = self._lumi_lines()
 
+    def _streams(self, streams):
+        streams = list(
+            filter(lambda stream: len(stream.lines) > 0,
+                   sorted(streams, key=lambda stream: stream.name)))
+
+        names = [stream.name for stream in streams]
+        assert len(streams) == len(
+            unique(names)), "Multiple streams with same name found in streams."
+        return streams
+
     def _lines(self):
         """Function to return flat list of DecisionLines from streams"""
         lines = []
@@ -171,6 +179,17 @@ class Streams(object):
             print(" lumi_lines:   ", [l.name for l in stream.lumi_lines])
             print(" raw_banks:    ", stream.raw_banks)
 
+    def get(self, stream_name):
+        filtered = list(filter(lambda s: s.name is stream_name, self.streams))
+
+        if len(filtered) == 1:
+            return filtered[0]
+        elif len(filtered) == 0:
+            raise ConfigurationError(f"{stream_name} not found in streams.")
+        else:
+            raise ConfigurationError(
+                f"Multiple streams with name {stream_name} found in streams.")
+
 
 def make_default_streams(lines):
     stream = Stream(name="default", lines=lines, detectors=DETECTORS)