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