depq 1.5.5

此实现的功能和优点：

• 完全线程安全
• 可通过pickling或json序列化
• 优先级值可以是int/float、numpy类型、字符串或 任何其他可比类型你选择！
• popfirst（）和poplast（）具有o（1）性能，而不是 以对数时间运行，如在标准depq或其他 堆派生结构
• 自然也很快，因为deque对象是用c实现的
• 优先级相等的项按它们的顺序排序 最初添加
• 可以删除特定项目或更改其优先级
• 在o（1）中使用“in”运算符进行成员资格测试 通过计数（item）获取depq中项目的频率

实施：

• 优先级总是按正确的顺序排列，因此，二进制搜索 执行此操作是为了找到要插入新索引的正确索引 指定优先级时的项。通常，这会导致 o（n logn）通过insert添加项时的性能（项，优先级） 其中self.high（）>；priority>；self.low（），因为deque（作为 双链表）随机访问是o（n）。

  不过，事实上这不是我能做到的 将二进制搜索修改为 内部装置同时旋转。

示例：

>>> from textwrap import fill  # For nice wrapped printing
>>> from depq import DEPQ
>>>
>>> # Defaults. If iterable is not None, extend(iterable) will be
>>> # called (example below). If maxlen is not None, abs(int(maxlen))
>>> # will become the length limit. If a maxlen is set and an item
>>> # is added with a priority > lowest prioritized item, it will be
>>> # added and the last item will be popped. After instantiation, the
>>> # maxlen can be retrieved with maxlen() and set with set_maxlen(length).
>>> depq = DEPQ(iterable=None, maxlen=None)
>>>
>>> # Add some characters with their ordinal
>>> # values as priority and keep count
>>> for c in 'AN_ERRONEOUS_STRING':
...     count = list(  # This is hacky and not important, skip next 4 lines :)
...         x + 1 if '{} #{}'.format(c, x + 1) in depq
...         else next(iter(())) if x != 0 else 0
...         for x in range(len(depq) + 1)
...     )[-1]
...
...     depq.insert('{} #{}'.format(c, count + 1), ord(c))  # item, priority
...
>>> print(fill(str(depq), 77))
DEPQ([('_ #1', 95), ('_ #2', 95), ('U #1', 85), ('T #1', 84), ('S #1', 83),
('S #2', 83), ('R #1', 82), ('R #2', 82), ('R #3', 82), ('O #1', 79), ('O
#2', 79), ('N #1', 78), ('N #2', 78), ('N #3', 78), ('I #1', 73), ('G #1',
71), ('E #1', 69), ('E #2', 69), ('A #1', 65)])
>>>
>>> # As you can see items with equal priorities are sorted in the order
>>> # they were originally added. Also note DEPQ root (depq[0]) is highest
>>> # priority like a max heap.
>>>
>>> depq.first()
'_ #1'
>>> depq.last()
'A #1'
>>> depq.high()
95
>>> depq.low()
65
>>> depq[7]  # Returns tuple(item, priority)
('R #2', 82)
>>>
>>> depq.poplast()
('A #1', 65)
>>> depq.last()
'E #2'
>>>
>>> depq.size()  # Alias for len(DEPQ)
18
>>> depq.is_empty()
False
>>> depq.clear()
>>> depq.is_empty()
True
>>>
>>> # Extend any length iterable of iterables of length >= 2
>>> depq.extend([('bar', 1, 'arbitrary'), (None, 5), ('foo', 2, 'blah')])
>>> depq
DEPQ([(None, 5), ('foo', 2), ('bar', 1)])
>>>
>>> depq.clear()
>>>
>>> depq.addfirst('starter')  # For an empty DEPQ, addfirst & addlast are
>>>                           # functionally identical; they add item to DEPQ
>>> depq                      # with given priority, or default 0
DEPQ([('starter', 0)])
>>>
>>> depq.addfirst('high', depq.high() + 1)
>>> depq.addlast('low', depq.low() - 1)
>>> depq
DEPQ([('high', 1), ('starter', 0), ('low', -1)])
>>>
>>> depq.addfirst('higher')  # Default priority DEPQ.high()
>>> depq.addlast('lower')  # Default priority DEPQ.low()
>>> depq
DEPQ([('higher', 1), ('high', 1), ('starter', 0), ('low', -1), ('lower', -1)])
>>>
>>> depq.addfirst('highest', 0)  # Invalid priority raises exception
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python34\lib\depq.py", line 340, in addfirst
    raise ValueError('Priority must be >= '
ValueError: Priority must be >= highest priority.
>>>
>>> del depq[0]  # As does del
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python34\lib\depq.py", line 639, in __delitem__
    raise NotImplementedError('Items cannot be deleted by '
NotImplementedError: Items cannot be deleted by referencing arbitrary indices.
>>>
>>> depq.clear()
>>> depq.count(None)
0
>>> for i in range(10):
...     depq.insert(None, i)
...
>>> print(fill(str(depq), 77))
DEPQ([(None, 9), (None, 8), (None, 7), (None, 6), (None, 5), (None, 4),
(None, 3), (None, 2), (None, 1), (None, 0)])
>>>
>>> None in depq
True
>>> depq.count(None)
10
>>> depq.remove(None)  # Removes item from DEPQ, default # of removals is 1
[(None, 0)]
>>>
>>> print(fill(str(depq), 77))
DEPQ([(None, 9), (None, 8), (None, 7), (None, 6), (None, 5), (None, 4),
(None, 3), (None, 2), (None, 1)])
>>>
>>> depq.remove(None, 4)  # As you see, returns list of tuple(item, priority)
[(None, 1), (None, 2), (None, 3), (None, 4)]
>>> print(fill(str(depq), 77))
DEPQ([(None, 9), (None, 8), (None, 7), (None, 6), (None, 5)])
>>>
>>> depq[None] = 7  # Alias for DEPQ.insert(item, priority)
>>> print(fill(str(depq), 77))
DEPQ([(None, 9), (None, 8), (None, 7), (None, 7), (None, 6), (None, 5)])
>>>
>>> depq.elim(None)  # This simply calls DEPQ.remove(item, -1)
[(None, 5), (None, 6), (None, 7), (None, 7), (None, 8), (None, 9)]
>>> print(fill(str(depq), 77))
DEPQ([])
>>>
>>> import pickle  # Pickling won't work if items aren't picklable
>>> import json  # JSON won't work if items aren't JSON serializable
>>>
>>> for i in range(5):
...     depq.insert([i], i)  # Unhashable types allowed but don't mutate them!
...
>>> depq
DEPQ([([4], 4), ([3], 3), ([2], 2), ([1], 1), ([0], 0)])
>>>
>>> binary_depq = pickle.dumps(depq)
>>> print(fill(str(binary_depq), 77))
b'\x80\x03cdepq\nDEPQ\nq\x00)\x81q\x01}q\x02(X\x05\x00\x00\x00itemsq\x03}q\x0
4(X\x03\x00\x00\x00[1]q\x05K\x01X\x03\x00\x00\x00[3]q\x06K\x01X\x03\x00\x00\x
00[2]q\x07K\x01X\x03\x00\x00\x00[4]q\x08K\x01X\x03\x00\x00\x00[0]q\tK\x01uX\x
04\x00\x00\x00dataq\nccollections\ndeque\nq\x0b]q\x0c(]q\rK\x04aK\x04\x86q\x0
e]q\x0fK\x03aK\x03\x86q\x10]q\x11K\x02aK\x02\x86q\x12]q\x13K\x01aK\x01\x86q\x
14]q\x15K\x00aK\x00\x86q\x16e\x85q\x17Rq\x18X\x05\x00\x00\x00startq\x19K\x00u
b.'
>>>
>>> json_depq = json.dumps(depq.to_json())
>>> print(fill(json_depq, 77))
{"items": {"[1]": 1, "[3]": 1, "[2]": 1, "[4]": 1, "[0]": 1}, "data": [[[4],
4], [[3], 3], [[2], 2], [[1], 1], [[0], 0]], "start": 0}
>>>
>>> depq_from_pickle = pickle.loads(binary_depq)
>>> depq_from_json = DEPQ.from_json(json_depq)  # Classmethod returns new DEPQ
>>>
>>> depq
DEPQ([([4], 4), ([3], 3), ([2], 2), ([1], 1), ([0], 0)])
>>> depq_from_pickle
DEPQ([([4], 4), ([3], 3), ([2], 2), ([1], 1), ([0], 0)])
>>> depq_from_json
DEPQ([([4], 4), ([3], 3), ([2], 2), ([1], 1), ([0], 0)])
>>>

注：

• depq中的项也与它们的频率一起存储在 分开dict进行o（1）查找。如果项是不可哈希的，则repr（） 而不是存储该项的。所以'item in depq'会检查 dict for item，如果引发typeerror，它将尝试repr（item）。
• 此实现在线性时间的中间插入 教科书depq是o（log n）。但是在实际的用例中 运行时间的无穷小增长是无关紧要的，特别是当 有人认为，与 其他两个主操作popfirst（）和poplast（）现在 在恒定的时间内发生。