python date of the previous month

Question

I am trying to get the date of the previous month with python  Here is what i ve tried   str  time strftime   Y       str  int time strftime   m   -1     However  this way is bad for 2 reasons  First it returns 20122 for the February of 2012  instead of 201202  and secondly it will return 0 instead of 12 on January   I have solved this trouble in bash with  echo   date -d 3 month ago     G m d     I think that if bash has a built-in way for this purpose  then python  much more equipped  should provide something better than forcing writing one s own script to achieve this goal  Of course i could do something like   if int time strftime   m       1      return  12  else      if int time strftime   m     lt  10          return  0  str time strftime   m  -1      else          return str time strftime   m   -1    I have not tested this code and i don t want to use it anyway  unless I can t find any other way     Thanks for your help

User · Answer

With the Pendulum very complete library  we have the subtract method  and not  subStract     import pendulum today   pendulum datetime today      2020  january lastmonth   today subtract months 1  lastmonth strftime   Y m      201912    We see that it handles jumping years   The reverse equivalent is add   https   pendulum eustace io docs  addition-and-subtraction

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def prev month date datetime datetime today         if date month    1          return date replace month 12 year date year-1      else          try              return date replace month date month-1          except ValueError              return prev month date date replace day date day-1

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For someone who got here and looking to get both the first and last day of the previous month   from datetime import date  timedelta  last day of prev month   date today   replace day 1  - timedelta days 1   start day of prev month   date today   replace day 1  - timedelta days last day of prev month day     For printing results print  First day of prev month    start day of prev month  print  Last day of prev month    last day of prev month    Output   First day of prev month  2019-02-01 Last day of prev month  2019-02-28

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Building off the comment of  J F  Sebastian  you can chain the replace   function to go back one  month   Since a month is not a constant time period  this solution tries to go back to the same date the previous month  which of course does not work for all months  In such a case  this algorithm defaults to the last day of the prior month   from datetime import datetime  timedelta  d   datetime 2012  3  31    A problem date as an example    last day of last month one month ago    d replace day 1  - timedelta days 1   try        try to go back to same day last month     one month ago   one month ago replace day d day  except ValueError      pass print  one month ago   0   format one month ago     Output   one month ago  2012-02-29 00 00 00

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There is a high level library dateparser that can determine the past date given natural language  and return the corresponding Python datetime object  from dateparser import parse parse  4 months ago

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import pandas as pd  lastmonth   int pd to datetime  quot today quot   strftime  quot  Y m quot   -1  print lastmonth    202101

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Simple  one liner  import datetime as dt previous month    dt date today   replace day 1  - dt timedelta days 1   month

User · Answer

You should use dateutil  With that  you can use relativedelta  it s an improved version of timedelta    gt  gt  gt  import datetime   gt  gt  gt  import dateutil relativedelta  gt  gt  gt  now   datetime datetime now    gt  gt  gt  print now 2012-03-15 12 33 04 281248  gt  gt  gt  print now   dateutil relativedelta relativedelta months -1  2012-02-15 12 33 04 281248

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Just for fun  a pure math answer using divmod  Pretty inneficient because of the multiplication  could do just as well a simple check on the number of month  if equal to 12  increase year  etc   year   today year month   today month  nm   list divmod year   12   month   1  12   if nm 1     0      nm 1    12     nm 0  -  1 pm   list divmod year   12   month - 1  12   if pm 1     0      pm 1    12     pm 0  -  1  next month   nm previous month   pm

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from datetime import date  timedelta  first day of current month   date today   replace day 1  last day of previous month   first day of current month - timedelta days 1   print  Previous month    last day of previous month month   Or   from datetime import date  timedelta  prev   date today   replace day 1  - timedelta days 1  print prev month

User · Answer

datetime and the datetime timedelta classes are your friend    find today  use that to find the first day of this month  use timedelta to backup a single day  to the last day of the previous month  print the YYYYMM string you re looking for    Like this    import datetime  today   datetime date today    first   today replace day 1   lastMonth   first - datetime timedelta days 1   print lastMonth strftime   Y m      201202 is printed

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Building on bgporter s answer   def prev month range when   None           Return  previous month s start date  previous month s end date          if not when            Default to today          when   datetime datetime today         Find previous month  https   stackoverflow com a 9725093 564514       Find today      first   datetime date day 1  month when month  year when year        Use that to find the first day of this month      prev month end   first - datetime timedelta days 1      prev month start   datetime date day 1  month  prev month end month  year  prev month end year        Return previous month s start and end dates in YY-MM-DD format      return  prev month start strftime   Y- m- d    prev month end strftime   Y- m- d

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Its very easy and simple  Do this  from dateutil relativedelta import relativedelta from datetime import datetime  today date   datetime today   print  todays date time   s   today date  one month ago   today date - relativedelta months 1  print  one month ago date time   s    one month ago print  one month ago date   s    one month ago date     Here is the output   python2 7 main py  todays date time  2016-09-06 02 13 01 937121 one month ago date time  2016-08-06 02 13 01 937121 one month ago date  2016-08-06

[python] python date of the previous month

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