use a defaultdict for SuperSequences instead of a regular dict

lib/sequences.py

@@ -3,6 +3,7 @@ from .structures import *
 import matplotlib.pyplot as pp
 from .plotdefs import Plotter
 import copy
+from collections import defaultdict
 import pathlib
 import toml
 import shutil
@@ -49,6 +50,18 @@ def max_n(generator, default=None):
             x0 = x
     return default if x0 is None else x0
 
+def _dict_to_defaultdict(D: dict) -> defaultdict:
+    valtype = type(list(D.values())[0])
+    if not all(isinstance(v, valtype) for v in D.values()):
+        raise Exception(
+            "dict_to_defaultdict:"
+            " can only construct from homogeneously valued dicts"
+        )
+    DD = defaultdict(valtype)
+    for k, v in D.items():
+        DD[k] = v
+    return DD
+
 class SuperSequence:
     """
     Sequence of labeled Sequences. Mostly for visualization purposes.
@@ -57,7 +70,7 @@ class SuperSequence:
     ------
     outdir : pathlib.Path
     name : str
-    sequences : dict[str, Sequence]
+    sequences : connections.defaultdict[str, Sequence]
     defaults : ConnectionLayout
     """
 
@@ -76,7 +89,10 @@ class SuperSequence:
         """
         self.outdir = outdir
         self.name = name
-        self.sequences = dict() if sequences is None else sequences
+        self.sequences = (
+            defaultdict(Sequence) if sequences is None
+            else _dict_to_defaultdict(sequences)
+        )
         self.params = dict() if params is None else params
         self.defaults = defaults