add ChainMap sample

michaelliao · michaelliao · commit b2d706860535 · 2018-10-12T11:23:37.000+08:00
diff --git a/samples/commonlib/use_chainmap.py b/samples/commonlib/use_chainmap.py
@@ -0,0 +1,20 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+from collections import ChainMap
+import os, argparse
+
+defaults = {
+    'color': 'red',
+    'user': 'guest'
+}
+
+parser = argparse.ArgumentParser()
+parser.add_argument('-u', '--user')
+parser.add_argument('-c', '--color')
+namespace = parser.parse_args()
+command_line_args = { k: v for k, v in vars(namespace).items() if v }
+
+combined = ChainMap(command_line_args, os.environ, defaults)
+print('color=%s' % combined['color'])
+print('user=%s' % combined['user'])
