visidata: fix hidecol and add menu entry

config/visidata/plugins/hidecol.py

@@ -10,32 +10,39 @@ def hide_empty_and_superfluous_cols(sheet):
     Given a sheet, hides columns that are empty or superfluous (contain the same
     value in every row).
     """
-    # Count how many columns were hidden
     counter = 0
-    # Check each column for being empty or superfluous
-    for col in sheet.visibleCols:
-        # If the column is not hidden
-        if col.width and col.width > 0:
-            # Check if the column is empty (all cells are empty or None)
-            if all([col.getValue(row) in (None, "", "null") for row in sheet.rows]):
-                # Hide the column
-                col.width = 0
-                counter += 1
-                # Skip the next check for same values since all cells are empty or None
+    # Iterate over a snapshot; hiding columns mutates sheet.visibleCols.
+    for col in list(sheet.visibleCols):
+        if not col.width or col.width <= 0:
+            continue
+
+        # Single pass over rows: track emptiness and distinct non-empty values.
+        all_empty = True
+        nonempty_vals = set()
+        for row in sheet.rows:
+            v = col.getValue(row)
+            if v in (None, "", "null"):
                 continue
+            all_empty = False
+            nonempty_vals.add(str(v))
+            if len(nonempty_vals) > 1:
+                break
 
-            # Check if the column is superfluous (contains the same value in every row)
-            # collect all values in the column as strings
-            values = set([f'{col.getValue(row)}' for row in sheet.rows if col.getValue(row) not in (None, "", "null")])
-            # If there is only one value in the column
-            if len(values) == 1:
-                # Hide the column
-                col.width = 0
-                counter += 1
+        if all_empty or len(nonempty_vals) == 1:
+            col.width = 0
+            counter += 1
 
+    if counter:
         vd.status(f"Hid {counter} empty/superfluous columns.")
     else:
         vd.status("No empty/superfluous columns to hide.")
 
-Sheet.addCommand(None, "tke-hidecol", "sheet.hide_empty_and_superfluous_cols()")
+Sheet.addCommand(
+    None,
+    "tke-hidecol",
+    "sheet.hide_empty_and_superfluous_cols()",
+    helpstr="Hide columns that are empty or have the same value in every row.",
+)
 
+# Make the command discoverable in the top menu bar (no default keybinding).
+vd.addMenuItem("Column", "Hide", "empty/superfluous columns", "tke-hidecol")