如何根据开始和结束获取for循环中的日期列表？

Question

I want to get a list of unique yyyy-mm-01 for a range between a start and end date using a for loop. This is the code I have:

import datetime
from datetime import timedelta, date

start=date(2017,4,1)
end=(datetime.date.today().replace(day=1)) - datetime.timedelta(days=1) #last completed month

def daterange(start, end):
    for n in range(int((end - start).days)):
        yield start + timedelta(n)

for single_date in daterange(start, end):
    myset = str(single_date.strftime("%Y-%m-01"))
    print(myset)

The issue is that my result looks like this:
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-04-01
2017-05-01

I tried adding set() but it still shows the redundant dates. How do I solve for that?

Answer 1

dates = set()
for single_date in daterange(start, end):
    dates.add(single_date.strftime("%Y-%m-01"))

print(sorted(list(dates)))

Answer 2

The issue is you aren't actually making use of your set to check if you've seen a date before:

myset = set()
for single_date in daterange(start, end):
    mydate = str(single_date.strftime("%Y-%m-01"))
    if mydate not in myset:
        print(mydate)
        myset.add(mydate)

Answer 3

import datetime
from datetime import timedelta, date
from dateutil.relativedelta import relativedelta

start=date(2017,4,1)
end=(datetime.date.today().replace(day=1)) - datetime.timedelta(days=1) #last completed month

lst = []
current_date = start
while current_date < end:
    current_date = current_date.replace(day=1) + relativedelta(months=1)
    lst.append(current_date)

print(lst)

Answer 4

I strongly suggest you to use dateutils module for obtaining recurring dates like this. You can install it using the cmd pip install python-dateutil

>>> from dateutil.rrule import rrule, MONTHLY
>>>
>>> start=date(2017,4,1)
>>> end=(datetime.date.today().replace(day=1)) - datetime.timedelta(days=1)
>>> res = list(d.strftime("%Y-%m-%d") for d in rrule(dtstart=start, until=end, freq=MONTHLY))
>>> pprint(res)
['2017-04-01',
 '2017-05-01',
 '2017-06-01',
 '2017-07-01',
 '2017-08-01',
 '2017-09-01',
 '2017-10-01',
 '2017-11-01',
 '2017-12-01',
 '2018-01-01',
 '2018-02-01',
 '2018-03-01',
 '2018-04-01',
 '2018-05-01',
 '2018-06-01',
 '2018-07-01',
 '2018-08-01',
 '2018-09-01',
 '2018-10-01',
 '2018-11-01',
 '2018-12-01',
 '2019-01-01',
 '2019-02-01',
 '2019-03-01',
 '2019-04-01',
 '2019-05-01',
 '2019-06-01',
 '2019-07-01',
 '2019-08-01',
 '2019-09-01',
 '2019-10-01',
 '2019-11-01',
 '2019-12-01',
 '2020-01-01',
 '2020-02-01',
 '2020-03-01',
 '2020-04-01',
 '2020-05-01',
 '2020-06-01',
 '2020-07-01']