diff options
| -rw-r--r-- | Doc/library/collections.rst | 12 | ||||
| -rw-r--r-- | Lib/collections/__init__.py | 7 | ||||
| -rw-r--r-- | Lib/test/test_collections.py | 4 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Library/2021-03-08-22-14-37.bpo-43245.nXL-MC.rst | 1 |
4 files changed, 18 insertions, 6 deletions
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst index 540db20..723c9da 100644 --- a/Doc/library/collections.rst +++ b/Doc/library/collections.rst @@ -72,19 +72,23 @@ The class can be used to simulate nested scopes and is useful in templating. be modified to change which mappings are searched. The list should always contain at least one mapping. - .. method:: new_child(m=None) + .. method:: new_child(m=None, **kwargs) Returns a new :class:`ChainMap` containing a new map followed by all of the maps in the current instance. If ``m`` is specified, it becomes the new map at the front of the list of mappings; if not specified, an empty dict is used, so that a call to ``d.new_child()`` - is equivalent to: ``ChainMap({}, *d.maps)``. This method is used for - creating subcontexts that can be updated without altering values in any - of the parent mappings. + is equivalent to: ``ChainMap({}, *d.maps)``. If any keyword arguments + are specified, they update passed map or new empty dict. This method + is used for creating subcontexts that can be updated without altering + values in any of the parent mappings. .. versionchanged:: 3.4 The optional ``m`` parameter was added. + .. versionchanged:: 3.10 + Keyword arguments support was added. + .. attribute:: parents Property returning a new :class:`ChainMap` containing all of the maps in 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 @@ class ChainMap(_collections_abc.MutableMapping): __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 @@ class TestChainMap(unittest.TestCase): 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)) diff --git a/Misc/NEWS.d/next/Library/2021-03-08-22-14-37.bpo-43245.nXL-MC.rst b/Misc/NEWS.d/next/Library/2021-03-08-22-14-37.bpo-43245.nXL-MC.rst new file mode 100644 index 0000000..394318f --- /dev/null +++ b/Misc/NEWS.d/next/Library/2021-03-08-22-14-37.bpo-43245.nXL-MC.rst @@ -0,0 +1 @@ +Add keyword arguments support to ``ChainMap.new_child()``.
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