40 lines
1.3 KiB
Python
40 lines
1.3 KiB
Python
# 假如我们有一个记录需要进行分组
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rows = [
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{"address": "5412 N CLARK", "date": "07/01/2012"},
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{"address": "5148 N CLARK", "date": "07/04/2012"},
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{"address": "5800 E 58TH", "date": "07/02/2012"},
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{"address": "2122 N CLARK", "date": "07/03/2012"},
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{"address": "5645 N RAVENSWOOD", "date": "07/02/2012"},
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{"address": "1060 W ADDISON", "date": "07/02/2012"},
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{"address": "4801 N BROADWAY", "date": "07/01/2012"},
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{"address": "1039 W GRANVILLE", "date": "07/04/2012"},
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]
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# 如果我们想按日期进行分组，那itertools里的groupby会很好用
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from operator import itemgetter
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from itertools import groupby
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# 因为groupby只能检查连续的项，所以我们先对列表进行排序
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rows.sort(key=itemgetter("date"))
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print(rows)
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# 然后我们进行分组操作：
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for date, items in groupby(rows, itemgetter("date")):
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print(date)
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for i in items:
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print(' ', i)
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# groupby每次返回的是一个值（分组名称）和一个子迭代器（组内数据）
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# 当然如果是单纯的分组，一键多值字典是个好东西
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from collections import defaultdict
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data = defaultdict(list)
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for item in rows:
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data[item["date"]].append(item)
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print(data)
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# 在不考虑内存开销的情况下，这东西比先排序再groupby快
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