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# -*- coding: utf-8 -*-
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#
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from itertools import chain
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from .utils import lazyproperty
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class Stack(list):
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def is_empty(self):
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return len(self) == 0
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@property
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def top(self):
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if self.is_empty():
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return None
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return self[-1]
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@property
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def bottom(self):
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if self.is_empty():
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return None
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return self[0]
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def size(self):
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return len(self)
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def push(self, item):
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self.append(item)
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class QuerySetChain:
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def __init__(self, querysets):
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self.querysets = querysets
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@lazyproperty
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def querysets_counts(self):
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counts = [s.count() for s in self.querysets]
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return counts
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def count(self):
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return self.total_count
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@lazyproperty
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def total_count(self):
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return sum(self.querysets_counts)
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def __iter__(self):
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self._chain = chain(*self.querysets)
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return self
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def __next__(self):
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return next(self._chain)
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def __getitem__(self, ndx):
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querysets_count_zip = zip(self.querysets, self.querysets_counts)
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length = 0 # 加上本数组后的大数组长度
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pre_length = 0 # 不包含本数组的大数组长度
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items = [] # 返回的值
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loop = 0
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if isinstance(ndx, slice):
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ndx_start = ndx.start or 0
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ndx_stop = ndx.stop or self.total_count
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ndx_step = ndx.step or 1
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else:
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ndx_start = ndx
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ndx_stop, ndx_step = None, None
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for queryset, count in querysets_count_zip:
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length += count
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loop += 1
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# 取当前数组的start角标, 存在3中情况
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# 1. start角标在当前数组
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if length > ndx_start >= pre_length:
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start = ndx_start - pre_length
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# print("[loop {}] Start is: {}".format(loop, start))
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if ndx_step is None:
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return queryset[start]
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# 2. 不包含当前数组，因为起始已经超过了当前数组的长度
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elif ndx_start >= length:
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pre_length += count
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continue
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# 3. 不在当前数组，但是应该从当前数组0开始计算
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else:
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start = 0
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# 可能取单个值, ndx_stop 为None, 不应该再找
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if ndx_stop is None:
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pre_length += count
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continue
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# 取当前数组的stop角标, 存在2中情况
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# 不存在第3中情况是因为找到了会提交结束循环
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# 1. 结束角标小于length代表 结束位在当前数组上
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if ndx_stop < length:
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stop = ndx_stop - pre_length
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# 2. 结束位置包含改数组到了最后
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else:
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stop = count
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# print("[loop {}] Slice: {} {} {}".format(loop, start, stop, ndx_step))
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items.extend(list(queryset[slice(start, stop, ndx_step)]))
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pre_length += count
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# 如果结束再当前数组，则结束循环
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if ndx_stop < length:
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break
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return items
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