implement config.setdefault

gallery_dl/config.py

@@ -68,6 +68,18 @@ def set(keys, value):
             conf = temp
     conf[keys[-1]] = value
 
+def setdefault(keys, value):
+    """Set the value of property 'key' if it doesn't exist"""
+    conf = _config
+    for k in keys[:-1]:
+        try:
+            conf = conf[k]
+        except KeyError:
+            temp = {}
+            conf[k] = temp
+            conf = temp
+    return conf.setdefault(keys[-1], value)
+
 
 # --------------------------------------------------------------------
 # internals

test/test_config.py

@@ -36,6 +36,12 @@ class TestConfig(unittest.TestCase):
         self.assertEqual(config.get(["b", "c"]), [1, 2, 3])
         self.assertEqual(config.get(["e", "f", "g"]), 234)
 
+    def test_setdefault(self):
+        config.setdefault(["b", "c"], [1, 2, 3])
+        config.setdefault(["e", "f", "g"], value=234)
+        self.assertEqual(config.get(["b", "c"]), "text")
+        self.assertEqual(config.get(["e", "f", "g"]), 234)
+
     def test_interpolate(self):
         self.assertEqual(config.interpolate(["a"]), "1")
         self.assertEqual(config.interpolate(["b", "a"]), "1")