Use eval to compute cost

config.yaml

@@ -63,6 +63,7 @@ beetslabels:
       # or: "label:a , label:b"
       # in the future? concat: ["label:a", "label:b"]
       query: "label:effortless"
+      sort: "effortless + exercise"
 
 smartplaylist:
   relative_to: ~/Music/0beets_playlists

plugins/playlists.py

@@ -5,6 +5,8 @@ from beets.dbcore.query import SlowFieldSort
 from .labels import LABELS_FIELD_NAME
 
 import json
+import ast
+import re
 
 playlist_config = {}
 
@@ -12,20 +14,72 @@ def initialize_playlists(playlists):
     for playlist in playlists:
         pl_name = playlist["name"]
         query = [playlist["query"], ",", f"label:{pl_name}"]
-        playlist_config[pl_name] = query
+        sort_expr = playlist.get("sort", None)
+        playlist_config[pl_name] = {
+            "query": query,
+            "sort": sort_expr
+        }
 
 def valid_playlist(playlist_name):
     return playlist_name in playlist_config
 
 def expand_playlist_query(playlist_name):
-    print(playlist_config[playlist_name])
-    return playlist_config[playlist_name]
+    return playlist_config[playlist_name]["query"]
+
+def get_sort_expression(playlist_name):
+    """Get the sort expression for a playlist, or None if not defined."""
+    return playlist_config[playlist_name].get("sort")
+
+def extract_label_names(expression):
+    """Extract label names from a Python expression.
+
+    Returns a set of identifier names found in the expression.
+    """
+    try:
+        tree = ast.parse(expression, mode='eval')
+        label_names = set()
+
+        for node in ast.walk(tree):
+            if isinstance(node, ast.Name):
+                label_names.add(node.id)
+
+        return label_names
+    except SyntaxError:
+        return set()
+
+def evaluate_sort_expression(expression, labels):
+    """Evaluate a sort expression with label values.
+
+    Args:
+        expression: Python expression like "effortless + exercise * 2"
+        labels: Dict of label names to values
+
+    Returns:
+        The evaluated result, or a default value if evaluation fails.
+    """
+    if not expression:
+        return 0
+
+    # Extract label names from the expression
+    label_names = extract_label_names(expression)
+
+    # Build a namespace with label values (defaulting to 0 for missing labels)
+    namespace = {name: labels.get(name, 0) for name in label_names}
+
+    try:
+        # Evaluate with restricted builtins for safety
+        result = eval(expression, {"__builtins__": {}}, namespace)
+        return float(result) if result is not None else 0
+    except Exception:
+        # If evaluation fails, return 0
+        return 0
 
 class PlaylistValueSort(SlowFieldSort):
     def __init__(self, field, ascending=True, case_insensitive=True):
         super().__init__(field, ascending, case_insensitive)
 
         self.playlist_key = field[len("playlist:"):]
+        self.sort_expr = get_sort_expression(self.playlist_key)
 
     def sort(self, objs):
         def key(obj):
@@ -37,12 +91,19 @@ class PlaylistValueSort(SlowFieldSort):
 
             labels = json.loads(labels_json)
 
+            # If there's a sort expression, evaluate it
+            if self.sort_expr:
+                return evaluate_sort_expression(self.sort_expr, labels)
+
+            # Otherwise, use the old behavior:
+            # Check if there's a label with the playlist name
             if self.playlist_key in labels:
                 return labels[self.playlist_key]
 
+            # Sum all matching label values from the playlist query
             matching_labels = \
                 [label for label in labels
-                 if label in playlist_config[self.playlist_key]]
+                 if label in playlist_config[self.playlist_key]["query"]]
 
             if len(matching_labels) == 0:
                 return float('-inf') if self.ascending else float('inf')