Add config itemselector example

examples/providers/configuration/configuration_itemselector.py

@@ -0,0 +1,47 @@
+"""`Configuration` provider dynamic item selector.
+
+Details: https://github.com/ets-labs/python-dependency-injector/issues/274
+"""
+
+import dataclasses
+
+from dependency_injector import providers
+
+
+@dataclasses.dataclass
+class Foo:
+    option1: object
+    option2: object
+
+
+config = providers.Configuration(default={
+    'target': 'A',
+    'items': {
+        'A': {
+            'option1': 60,
+            'option2': 80,
+        },
+        'B': {
+            'option1': 10,
+            'option2': 20,
+        },
+    },
+})
+
+foo = providers.Factory(
+    Foo,
+    option1=config.items[config.target].option1,
+    option2=config.items[config.target].option2,
+)
+
+
+if __name__ == '__main__':
+    config.target.from_env('TARGET')
+    f = foo()
+    print(f.option1, f.option2)
+
+
+# $ TARGET=A python configuration_itemselector.py
+# 60 80
+# $ TARGET=B python configuration_itemselector.py
+# 10 20