add persistent config (storing dynamic changes in file)

confuse/core.py

@@ -720,4 +720,18 @@ def clear(self):
         self._lazy_prefix = []
 
 
+class PersistentConfig(Configuration):
+
+    def add(self, obj):
+        super(PersistentConfig, self).add(obj)
+
+        with open(self.user_config_path(), 'w') as f:
+            f.write(self.dump().strip())
+
+    def set(self, value):
+        super(PersistentConfig, self).set(value)
+
+        with open(self.user_config_path(), 'w') as f:
+            f.write(self.dump().strip())
+
 # "Validated" configuration views: experimental!

test/test_persistent_config.py

@@ -0,0 +1,24 @@
+import confuse
+import unittest
+
+
+class PersistentConfigTest(unittest.TestCase):
+
+    def test_add(self):
+        config = confuse.PersistentConfig('myapp', read=False)
+        config.add({'foo': False})
+        del config
+
+        config_test = confuse.Configuration('myapp', read=True)
+        yaml_dump = config_test.dump().strip()
+        assert yaml_dump == 'foo: no'
+
+    def test_set(self):
+        config = confuse.PersistentConfig('myapp', read=False)
+        config['s'] = 'string'
+        config.set({'abc': 6})
+        del config
+
+        config_test = confuse.Configuration('myapp', read=True)
+        yaml_dump = config_test.dump().strip()
+        assert yaml_dump == 'abc: 6\ns: string'