Refactor offline

This refactoring includes some slicing and performance improvement attempts.

The slicing is still experimental and has some flaws:

• fancy indexing over thousands of elements might be horrible slow, eg f.events.tracks[idx_list, 0] where idx_list is a huge list of indices
• trivial problem of iterating: for track in f.evens.tracks does not stop after the last element
• meaningless indexing: f.events[5][23][420] is simply f.events[420] since the index/slice is not chained but overwritten when propagated. We need custom checks whether it makes sense
  • events are flat lists, so [x][y] does not make sense, it should throw an error
  • f.events[5:23][4] should effectively be the same as f.events[9] due to chaining of slice/index

km3io/offline.py

@@ -233,14 +233,20 @@ class Header:
 
             n_values = len(values)
             n_fields = len(fields)
+
+            if n_values == 1 and n_fields == 0:
+                self._data[attribute] = _to_num(values[0])
+                continue
+
             n_max = max(n_values, n_fields)
             values += [None] * (n_max - n_values)
             fields += ["field_{}".format(i) for i in range(n_fields, n_max)]
 
+            Constructor = namedtuple(attribute, fields)
+
             if not values:
                 continue
 
-            Constructor = namedtuple(attribute, fields)
             self._data[attribute] = Constructor(
                 **{f: _to_num(v)
                    for (f, v) in zip(fields, values)})