python (3.11.7)
1 import collections
2 import itertools
3
4
5 # from jaraco.collections 3.5.1
6 class ESC[4;38;5;81mDictStack(ESC[4;38;5;149mlist, ESC[4;38;5;149mcollectionsESC[4;38;5;149m.ESC[4;38;5;149mabcESC[4;38;5;149m.ESC[4;38;5;149mMapping):
7 """
8 A stack of dictionaries that behaves as a view on those dictionaries,
9 giving preference to the last.
10
11 >>> stack = DictStack([dict(a=1, c=2), dict(b=2, a=2)])
12 >>> stack['a']
13 2
14 >>> stack['b']
15 2
16 >>> stack['c']
17 2
18 >>> len(stack)
19 3
20 >>> stack.push(dict(a=3))
21 >>> stack['a']
22 3
23 >>> set(stack.keys()) == set(['a', 'b', 'c'])
24 True
25 >>> set(stack.items()) == set([('a', 3), ('b', 2), ('c', 2)])
26 True
27 >>> dict(**stack) == dict(stack) == dict(a=3, c=2, b=2)
28 True
29 >>> d = stack.pop()
30 >>> stack['a']
31 2
32 >>> d = stack.pop()
33 >>> stack['a']
34 1
35 >>> stack.get('b', None)
36 >>> 'c' in stack
37 True
38 """
39
40 def __iter__(self):
41 dicts = list.__iter__(self)
42 return iter(set(itertools.chain.from_iterable(c.keys() for c in dicts)))
43
44 def __getitem__(self, key):
45 for scope in reversed(tuple(list.__iter__(self))):
46 if key in scope:
47 return scope[key]
48 raise KeyError(key)
49
50 push = list.append
51
52 def __contains__(self, other):
53 return collections.abc.Mapping.__contains__(self, other)
54
55 def __len__(self):
56 return len(list(iter(self)))
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