From 30a7bd9eb2effacb8ff4c80a10ab7156a243b9da Mon Sep 17 00:00:00 2001
From: Ian Lin <andylin514@gmail.com>
Date: Thu, 15 Dec 2016 17:32:57 +0800
Subject: [PATCH] path reducer

---
 flatten_dict/flatten_dict.py | 3 ++-
 flatten_dict/reducer.py      | 7 +++++++
 flatten_dict/tests.py        | 5 +++++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/flatten_dict/flatten_dict.py b/flatten_dict/flatten_dict.py
index 81f3a9b..3944c42 100644
--- a/flatten_dict/flatten_dict.py
+++ b/flatten_dict/flatten_dict.py
@@ -2,11 +2,12 @@
 
 import six
 
-from .reducer import tuple_reducer
+from .reducer import tuple_reducer, path_reducer
 
 
 REDUCER_DICT = {
     'tuple': tuple_reducer,
+    'path': path_reducer,
 }
 
 def flatten(d, reducer='tuple', inverse=False):
diff --git a/flatten_dict/reducer.py b/flatten_dict/reducer.py
index 8cd0428..93f7f10 100644
--- a/flatten_dict/reducer.py
+++ b/flatten_dict/reducer.py
@@ -3,3 +3,10 @@ def tuple_reducer(k1, k2):
         return (k2,)
     else:
         return k1 + (k2,)
+
+def path_reducer(k1, k2):
+    import os.path
+    if k1 is None:
+        return k2
+    else:
+        return os.path.join(k1, k2)
diff --git a/flatten_dict/tests.py b/flatten_dict/tests.py
index 01a8948..e74a5b7 100644
--- a/flatten_dict/tests.py
+++ b/flatten_dict/tests.py
@@ -38,3 +38,8 @@ def test_flatten_dict_inverse():
 
 def test_flatten_dict_with_reducer():
     assert flatten(normal_dict, reducer=tuple_reducer) == flat_normal_dict
+
+def test_flatten_dict_path():
+    from os.path import join
+    flat_path_dict = {join(*k): v for k, v in six.viewitems(flat_normal_dict)}
+    assert flatten(normal_dict, reducer='path') == flat_path_dict