Polish

Preparing for extraction of selection task into a function.

Analysis/plot_snapshot.py

@@ -33,13 +33,13 @@ def snapshot(k, ax, k1, ishape_last, reader_extr, reader_outer,
 
     dashed: boolean."""
     
+    assert k >= k1
+    
     if k == k1:
         ishape_first = 0
-    elif k > k1:
-        ishape_first = ishape_last[k - k1 - 1] + 1
     else:
-        print("bad k value")
-        return
+        # k > k1
+        ishape_first = ishape_last[k - k1 - 1] + 1
 
     ax.set_title(f"k = {k}", y = 1.05)