要重写一个函数以实现OrderedDict,可以按照以下步骤进行:
以下是一个示例实现:
from collections import defaultdict, deque
class OrderedDict:
def __init__(self):
self.dict = defaultdict()
self.linked_list = deque()
def __setitem__(self, key, value):
if key in self.dict:
self.dict[key] = value
self.linked_list.remove(key)
else:
self.dict[key] = value
self.linked_list.append(key)
def __getitem__(self, key):
if key in self.dict:
self.linked_list.remove(key)
self.linked_list.append(key)
return self.dict[key]
def __delitem__(self, key):
if key in self.dict:
del self.dict[key]
self.linked_list.remove(key)
def __iter__(self):
for key in self.linked_list:
yield key, self.dict[key]
def __reversed__(self):
for key in reversed(self.linked_list):
yield key, self.dict[key]
def popitem(self):
if self.linked_list:
key = self.linked_list.pop()
value = self.dict.pop(key)
return key, value
def clear(self):
self.dict.clear()
self.linked_list.clear()
# 测试
ordered_dict = OrderedDict()
ordered_dict['a'] = 1
ordered_dict['b'] = 2
ordered_dict['c'] = 3
print(dict(ordered_dict)) # {'a': 1, 'b': 2, 'c': 3}
del ordered_dict['b']
print(dict(ordered_dict)) # {'a': 1, 'c': 3}
for key, value in ordered_dict:
print(key, value) # a 1\n c 3
for key, value in reversed(ordered_dict):
print(key, value) # c 3\n a 1
print(ordered_dict.popitem()) # ('c', 3)
ordered_dict.clear()
print(dict(ordered_dict)) # {}
请注意,上述示例是一个简化的实现,仅用于说明重写函数以实现OrderedDict的基本思路。在实际应用中,还需要考虑更多的细节和边界情况。
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