Iterating through a range of dates in Python

Question

I have the following code to do this  but how can I do it better  Right now I think it s better than nested loops  but it starts to get Perl-one-linerish when you have a generator in a list comprehension    day count    end date - start date  days   1 for single date in  d for d in  start date   timedelta n  for n in range day count   if d  lt   end date       print strftime   Y- m- d   single date timetuple      Notes   I m not actually using this to print  That s just for demo purposes   The start date and end date variables are datetime date objects because I don t need the timestamps   They re going to be used to generate a report     Sample Output  For a start date of 2009-05-30 and an end date of 2009-06-09   2009-05-30 2009-05-31 2009-06-01 2009-06-02 2009-06-03 2009-06-04 2009-06-05 2009-06-06 2009-06-07 2009-06-08 2009-06-09

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Slightly different approach to reversible steps by storing range args in a tuple    def date range start  stop  step 1  inclusive False       day count    stop - start  days     if inclusive          day count    1      if step  gt  0          range args    0  day count  step      elif step  lt  0          range args    day count - 1  -1  step      else          raise ValueError  date range    step arg must be non-zero        for i in range  range args           yield start   timedelta days i

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For those who are interested in Pythonic functional way  from datetime import date  timedelta from itertools import count  takewhile  for d in takewhile lambda x  x lt  date 2009 6 9   map lambda x date 2009 5 30  timedelta days x   count          print d

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This might be more clear   from datetime import date  timedelta  start date   date 2019  1  1  end date   date 2020  1  1  delta   timedelta days 1  while start date  lt   end date      print  start date strftime   Y- m- d        start date    delta

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For completeness  Pandas also has a period range function for timestamps that are out of bounds   import pandas as pd  pd period range start  1 1 1626   end  1 08 1627   freq  D

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Numpy s arange function can be applied to dates   import numpy as np from datetime import datetime  timedelta d0   datetime 2009  1 1  d1   datetime 2010  1 1  dt   timedelta days   1  dates   np arange d0  d1  dt  astype datetime    The use of astype is to convert from numpy datetime64 to an array of datetime datetime objects

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Why are there two nested iterations  For me it produces the same list of data with only one iteration  for single date in  start date   timedelta n  for n in range day count        print      And no list gets stored  only one generator is iterated over  Also the  quot if quot  in the generator seems to be unnecessary  After all  a linear sequence should only require one iterator  not two  Update after discussion with John Machin  Maybe the most elegant solution is using a generator function to completely hide abstract the iteration over the range of dates  from datetime import timedelta  date  def daterange start date  end date       for n in range int  end date - start date  days            yield start date   timedelta n   start date   date 2013  1  1  end date   date 2015  6  2  for single date in daterange start date  end date       print single date strftime  quot  Y- m- d quot     NB  For consistency with the built-in range   function this iteration stops before reaching the end date  So for inclusive iteration use the next day  as you would with range

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This is the most human-readable solution I can think of   import datetime  def daterange start  end  step datetime timedelta 1        curr   start     while curr  lt  end          yield curr         curr    step

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import datetime from dateutil rrule import DAILY rrule  date datetime datetime 2019 1 10   date1 datetime datetime 2019 2 2   for i in rrule DAILY   dtstart date until date1        print i strftime   Y b d   sep   n     OUTPUT   2019Jan10 2019Jan11 2019Jan12 2019Jan13 2019Jan14 2019Jan15 2019Jan16 2019Jan17 2019Jan18 2019Jan19 2019Jan20 2019Jan21 2019Jan22 2019Jan23 2019Jan24 2019Jan25 2019Jan26 2019Jan27 2019Jan28 2019Jan29 2019Jan30 2019Jan31 2019Feb01 2019Feb02

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Can t  believe this question has existed for 9 years without anyone suggesting a simple recursive function   from datetime import datetime  timedelta  def walk days start date  end date       if start date  lt   end date          print start date strftime   Y- m- d            next date   start date   timedelta days 1          walk days next date  end date    demo start date   datetime 2009  5  30  end date     datetime 2009  6  9   walk days start date  end date    Output   2009-05-30 2009-05-31 2009-06-01 2009-06-02 2009-06-03 2009-06-04 2009-06-05 2009-06-06 2009-06-07 2009-06-08 2009-06-09   Edit   Now I can believe it -- see Does Python optimize tail recursion     Thank you Tim

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What about the following for doing a range incremented by days   for d in map  lambda x  startDate datetime timedelta days x   xrange   stopDate-startDate  days          Do stuff here    startDate and stopDate are datetime date objects   For a generic version   for d in map  lambda x  startTime x stepTime  xrange   stopTime-startTime  total seconds     stepTime total seconds            Do stuff here    startTime and stopTime are datetime date or datetime datetime object  both should be the same type  stepTime is a timedelta object   Note that  total seconds   is only supported after python 2 7 If you are stuck with an earlier version you can write your own function   def total seconds  td      return float td microseconds    td seconds   td days   24   3600    10  6    10  6

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import datetime  def daterange start  stop  step days 1       current   start     step   datetime timedelta step days      if step days  gt  0          while current  lt  stop              yield current             current    step     elif step days  lt  0          while current  gt  stop              yield current             current    step     else          raise ValueError  daterange   step days argument must not be zero    if   name         main         from pprint import pprint as pp     lo   datetime date 2008  12  27      hi   datetime date 2009  1  5      pp list daterange lo  hi        pp list daterange hi  lo  -1        pp list daterange lo  hi  7        pp list daterange hi  lo  -7         assert not list daterange lo  hi  -1       assert not list daterange hi  lo       assert not list daterange lo  hi  -7       assert not list daterange hi  lo  7

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Pandas is great for time series in general  and has direct support for date ranges   import pandas as pd daterange   pd date range start date  end date    You can then loop over the daterange to print the date   for single date in daterange      print  single date strftime   Y- m- d      It also has lots of options to make life easier  For example if you only wanted weekdays  you would just swap in bdate range  See http   pandas pydata org pandas-docs stable timeseries html generating-ranges-of-timestamps  The power of Pandas is really its dataframes  which support vectorized operations  much like numpy  that make operations across large quantities of data very fast and easy   EDIT  You could also completely skip the for loop and just print it directly  which is easier and more efficient   print daterange

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Here s code for a general date range function  similar to Ber s answer  but more flexible   def count timedelta delta  step  seconds in interval          Helper function for iterate   Finds the number of intervals in the timedelta         return int delta total seconds      seconds in interval   step     def range dt start  end  step 1  interval  day           Iterate over datetimes or dates  similar to builtin range         intervals   functools partial count timedelta   end - start   step       if interval     week           for i in range intervals 3600   24   7                yield start   datetime timedelta weeks i    step      elif interval     day           for i in range intervals 3600   24                yield start   datetime timedelta days i    step      elif interval     hour           for i in range intervals 3600                yield start   datetime timedelta hours i    step      elif interval     minute           for i in range intervals 60                yield start   datetime timedelta minutes i    step      elif interval     second           for i in range intervals 1                yield start   datetime timedelta seconds i    step      elif interval     millisecond           for i in range intervals 1   1000                yield start   datetime timedelta milliseconds i    step      elif interval     microsecond           for i in range intervals 1e-6                yield start   datetime timedelta microseconds i    step      else          raise AttributeError  Interval must be  week    day    hour   second                  microsecond  or  millisecond

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Why not try   import datetime as dt  start date   dt datetime 2012  12 1  end date   dt datetime 2012  12 5   total days    end date - start date  days   1  inclusive 5 days  for day number in range total days       current date    start date   dt timedelta days   day number   date       print current date

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from datetime import date timedelta delta   timedelta days 1  start   date 2020 1 1  end date 2020 9 1  loop date   start while loop date lt  end      print loop date      loop date  delta

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You can use Arrow  This is example from the docs  iterating over hours  from arrow import Arrow   gt  gt  gt  start   datetime 2013  5  5  12  30   gt  gt  gt  end   datetime 2013  5  5  17  15   gt  gt  gt  for r in Arrow range  hour   start  end           print repr r       lt Arrow  2013-05-05T12 30 00 00 00  gt   lt Arrow  2013-05-05T13 30 00 00 00  gt   lt Arrow  2013-05-05T14 30 00 00 00  gt   lt Arrow  2013-05-05T15 30 00 00 00  gt   lt Arrow  2013-05-05T16 30 00 00 00  gt   To iterate over days  you can use like this   gt  gt  gt  start   Arrow 2013  5  5   gt  gt  gt  end   Arrow 2013  5  5   gt  gt  gt  for r in Arrow range  day   start  end           print repr r    Didn t check if you can pass datetime date objects  but anyways Arrow objects are easier in general

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import datetime  def daterange start  stop  step datetime timedelta days 1   inclusive False       inclusive False to behave like range by default   if step days  gt  0      while start  lt  stop        yield start       start   start   step         not     don t modify object passed in if it s mutable         since this function is not restricted to         only types from datetime module   elif step days  lt  0      while start  gt  stop        yield start       start   start   step   if inclusive and start    stop      yield start         for date in daterange start date  end date  inclusive True     print strftime   Y- m- d   date timetuple      This function does more than you strictly require  by supporting negative step  etc  As long as you factor out your range logic  then you don t need the separate day count and most importantly the code becomes easier to read as you call the function from multiple places

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gt  pip install DateTimeRange  from datetimerange import DateTimeRange  def dateRange start  end  step           rangeList              time range   DateTimeRange start  end          for value in time range range datetime timedelta days step                rangeList append value strftime   m  d  Y            return rangeList      dateRange  2018-09-07    2018-12-25   7         Out 92          09 07 2018         09 14 2018         09 21 2018         09 28 2018         10 05 2018         10 12 2018         10 19 2018         10 26 2018         11 02 2018         11 09 2018         11 16 2018         11 23 2018         11 30 2018         12 07 2018         12 14 2018         12 21 2018

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I have a similar problem  but I need to iterate monthly instead of daily   This is my solution  import calendar from datetime import datetime  timedelta  def days in month dt       return calendar monthrange dt year  dt month  1   def monthly range dt start  dt end       forward   dt end  gt   dt start     finish   False     dt   dt start      while not finish          yield dt date           if forward              days   days in month dt              dt   dt   timedelta days days                          finish   dt  gt  dt end         else               tmp dt   dt replace day 1  - timedelta days 1              dt     tmp dt replace day dt day               finish   dt  lt  dt end   Example  1  date start   datetime 2016  6  1  date end   datetime 2017  1  1   for p in monthly range date start  date end       print p    Output  2016-06-01 2016-07-01 2016-08-01 2016-09-01 2016-10-01 2016-11-01 2016-12-01 2017-01-01   Example  2  date start   datetime 2017  1  1  date end   datetime 2016  6  1   for p in monthly range date start  date end       print p    Output  2017-01-01 2016-12-01 2016-11-01 2016-10-01 2016-09-01 2016-08-01 2016-07-01 2016-06-01

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You can generate a series of date between two dates using the pandas library simply and trustfully  import pandas as pd  print pd date range start  1 1 2010   end  1 08 2018   freq  M     You can change the frequency of generating dates by setting freq as  D  M  Q  Y  daily  monthly  quarterly  yearly

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for i in range 16       print datetime date today     datetime timedelta days i

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Show the last n days from today   import datetime for i in range 0  100       print  datetime date today     datetime timedelta i   isoformat      Output    2016-06-29 2016-06-30 2016-07-01 2016-07-02 2016-07-03 2016-07-04

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This function has some extra features    can pass a string matching the DATE FORMAT for start or end and it is converted to a date object can pass a date object for start or end error checking in case the end is older than the start  import datetime from datetime import timedelta   DATE FORMAT     Y  m  d   def daterange start  end         def convert date               try                    date   datetime datetime strptime date  DATE FORMAT                    return date date               except TypeError                    return date        def get date n               return datetime datetime strftime convert start    timedelta days n   DATE FORMAT         days    convert end  - convert start   days       if days  lt   0              raise ValueError  The start date must be before the end date          for n in range 0  days               yield get date n    start    2014 12 1  end    2014 12 31  print list daterange start  end    start    datetime date today   end    2015 12 1  print list daterange start  end

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Use the dateutil library   from datetime import date from dateutil rrule import rrule  DAILY  a   date 2009  5  30  b   date 2009  6  9   for dt in rrule DAILY  dtstart a  until b       print dt strftime   Y- m- d     This python library has many more advanced features  some very useful  like relative deltas   and is implemented as a single file  module  that s easily included into a project

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Using pendulum period  import pendulum  start   pendulum from format  2020-05-01    YYYY-MM-DD   formatter  alternative   end   pendulum from format  2020-05-02    YYYY-MM-DD   formatter  alternative    period   pendulum period start  end   for dt in period      print dt to date string

[python] Iterating through a range of dates in Python

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