Python：如何从日期列表计算日期范围？

Question

我有一组日期，比如：

['2011-02-27', '2011-02-28', '2011-03-01', '2011-04-12', '2011-04-13', '2011-06-08']

我该如何找到这些日期中连续的日期范围呢？在上面的例子中，应该得到的范围是：

[{"start_date": '2011-02-27', "end_date": '2011-03-01'},
 {"start_date": '2011-04-12', "end_date": '2011-04-13'},
 {"start_date": '2011-06-08', "end_date": '2011-06-08'}
]

谢谢。

Answer 1

试图偷偷修改GaretJax的编辑内容；）

def date_to_number(date):
  return datetime.date(*[int(i) for i in date.split('-')]).toordinal()

def number_to_date(number):
  return datetime.date.fromordinal(number).strftime('%Y-%m-%d')

def day_ranges(dates):
  day_numbers = set(date_to_number(d) for d in dates)
  start = None
  # We loop including one element guaranteed not to be in the set, to force the
  # closing of any range that's currently open.
  for n in xrange(min(day_numbers), max(day_numbers) + 2):
    if start == None:
      if n in day_numbers: start = n
    else:
      if n not in day_numbers: 
        yield {
          'start_date': number_to_date(start),
          'end_date': number_to_date(n - 1)
        }
        start = None

list(
  day_ranges([
    '2011-02-27', '2011-02-28', '2011-03-01',
    '2011-04-12', '2011-04-13', '2011-06-08'
  ])
)

Answer 2

from datetime import datetime, timedelta

dates = ['2011-02-27', '2011-02-28', '2011-03-01', '2011-04-12', '2011-04-13', '2011-06-08']
d = [datetime.strptime(date, '%Y-%m-%d') for date in dates]
test = lambda x: x[1] - x[0] != timedelta(1)
slices = [0] + [i+1 for i, x in enumerate(zip(d, d[1:])) if test(x)] + [len(dates)]
ranges = [{"start_date": dates[s], "end_date": dates[e-1]} for s, e in zip(slices, slices[1:])]

结果如下：

>>> pprint.pprint(ranges)
[{'end_date': '2011-03-01', 'start_date': '2011-02-27'},
 {'end_date': '2011-04-13', 'start_date': '2011-04-12'},
 {'end_date': '2011-06-08', 'start_date': '2011-06-08'}]

这个 slices 列表推导式会找出所有的索引位置，前一天的日期不是当前日期的前一天。然后在最前面加上 0，在最后面加上 len(dates)，这样每一段日期就可以用 dates[slices[i]:slices[i+1]-1] 来表示。

Answer 3

这个方法可以用，不过我对这个结果不太满意，打算找个更简洁的办法，然后再修改我的回答。 现在好了，这里有一个干净且有效的解决方案：

import datetime
import pprint

def parse(date):
    return datetime.date(*[int(i) for i in date.split('-')])

def get_ranges(dates):
    while dates:
        end = 1
        try:
            while dates[end] - dates[end - 1] == datetime.timedelta(days=1):
                end += 1
        except IndexError:
            pass

        yield {
            'start-date': dates[0],
            'end-date': dates[end-1]
        }
        dates = dates[end:]

dates = [
    '2011-02-27', '2011-02-28', '2011-03-01',
    '2011-04-12', '2011-04-13',
    '2011-06-08'
]

# Parse each date and convert it to a date object. Also ensure the dates
# are sorted, you can remove 'sorted' if you don't need it
dates = sorted([parse(d) for d in dates]) 

pprint.pprint(list(get_ranges(dates)))

还有相应的输出结果：

[{'end-date': datetime.date(2011, 3, 1),
  'start-date': datetime.date(2011, 2, 27)},
 {'end-date': datetime.date(2011, 4, 13),
  'start-date': datetime.date(2011, 4, 12)},
 {'end-date': datetime.date(2011, 6, 8),
  'start-date': datetime.date(2011, 6, 8)}]