bpo-43245: Add keyword argument support to ChainMap.new_child() (GH-24788)
diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
index 6404ea9..89c73bb 100644
--- a/Lib/collections/__init__.py
+++ b/Lib/collections/__init__.py
@@ -1010,12 +1010,15 @@ def copy(self):
__copy__ = copy
- def new_child(self, m=None): # like Django's Context.push()
+ def new_child(self, m=None, **kwargs): # like Django's Context.push()
'''New ChainMap with a new map followed by all previous maps.
If no map is provided, an empty dict is used.
+ Keyword arguments update the map or new empty dict.
'''
if m is None:
- m = {}
+ m = kwargs
+ elif kwargs:
+ m.update(kwargs)
return self.__class__(m, *self.maps)
@property
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index d1c305a..30303f0 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -249,6 +249,10 @@ def __contains__(self, key):
for k, v in dict(a=1, B=20, C=30, z=100).items(): # check get
self.assertEqual(d.get(k, 100), v)
+ c = ChainMap({'a': 1, 'b': 2})
+ d = c.new_child(b=20, c=30)
+ self.assertEqual(d.maps, [{'b': 20, 'c': 30}, {'a': 1, 'b': 2}])
+
def test_union_operators(self):
cm1 = ChainMap(dict(a=1, b=2), dict(c=3, d=4))
cm2 = ChainMap(dict(a=10, e=5), dict(b=20, d=4))