What is the standard way to add N seconds to datetime time in Python

Question

Given a datetime time value in Python  is there a standard way to add an integer number of seconds to it  so that 11 34 59   3   11 35 02  for example   These obvious ideas don t work    gt  gt  gt  datetime time 11  34  59    3 TypeError  unsupported operand type s  for     datetime time  and  int   gt  gt  gt  datetime time 11  34  59    datetime timedelta 0  3  TypeError  unsupported operand type s  for     datetime time  and  datetime timedelta   gt  gt  gt  datetime time 11  34  59    datetime time 0  0  3  TypeError  unsupported operand type s  for     datetime time  and  datetime time    In the end I have written functions like this   def add secs to time timeval  secs to add       secs   timeval hour   3600   timeval minute   60   timeval second     secs    secs to add     return datetime time secs    3600   secs   3600     60  secs   60    I can t help thinking that I m missing an easier way to do this though   Related   python time   timedelta equivalent

User · Answer

One little thing  might add clarity to override the default value for seconds   gt  gt  gt  b   a   datetime timedelta seconds 3000   gt  gt  gt  b datetime datetime 1  1  1  12  24  59

User · Answer

As others here have stated  you can just use full datetime objects throughout   from datetime import datetime  date  time  timedelta sometime   time 8 00    8am later    datetime combine date today    sometime    timedelta seconds 3   time     However  I think it s worth explaining why full datetime objects are required   Consider what would happen if I added 2 hours to 11pm   What s the correct behavior   An exception  because you can t have a time larger than 11 59pm   Should it wrap back around   Different programmers will expect different things  so whichever result they picked would surprise a lot of people   Worse yet  programmers would write code that worked just fine when they tested it initially  and then have it break later by doing something unexpected   This is very bad  which is why you re not allowed to add timedelta objects to time objects

User · Answer

You cannot simply add number to datetime because it s unclear what unit is used  seconds  hours  weeks     There is timedelta class for manipulations with date and time  datetime minus datetime gives timedelta  datetime plus timedelta gives datetime  two datetime objects cannot be added although two timedelta can   Create timedelta object with how many seconds you want to add and add it to datetime object    gt  gt  gt  from datetime import datetime  timedelta  gt  gt  gt  t   datetime now     timedelta seconds 3000   gt  gt  gt  print t  datetime datetime 2018  1  17  21  47  13  90244    There is same concept in C    std  chrono  duration

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You can use full datetime variables with timedelta  and by providing a dummy date then using time to just get the time value   For example   import datetime a   datetime datetime 100 1 1 11 34 59  b   a   datetime timedelta 0 3    days  seconds  then other fields  print a time    print b time      results in the two values  three seconds apart   11 34 59 11 35 02   You could also opt for the more readable  b   a   datetime timedelta seconds 3    if you re so inclined     If you re after a function that can do this  you can look into using addSecs below   import datetime  def addSecs tm  secs       fulldate   datetime datetime 100  1  1  tm hour  tm minute  tm second      fulldate   fulldate   datetime timedelta seconds secs      return fulldate time    a   datetime datetime now   time   b   addSecs a  300  print a  print b    This outputs    09 11 55 775695  09 16 55

User · Answer

If it s worth adding another file   dependency to your project  I ve just written a tiny little class that extends datetime time with the ability to do arithmetic   When you go past midnight  it wraps around zero   Now   What time will it be  24 hours from now  has a lot of corner cases  including daylight savings time  leap seconds  historical timezone changes  and so on   But sometimes you really do need the simple case  and that s what this will do   Your example would be written    gt  gt  gt  import datetime  gt  gt  gt  import nptime  gt  gt  gt  nptime nptime 11  34  59    datetime timedelta 0  3  nptime 11  35  2    nptime inherits from datetime time  so any of those methods should be usable  too   It s available from PyPi as nptime   non-pedantic time    or on GitHub  https   github com tgs nptime

User · Answer

For completeness  sake  here s the way to do it with arrow  better dates and times for Python    sometime   arrow now   abitlater   sometime shift seconds 3

User · Answer

In a real world environment it s never a good idea to work solely with time  always use datetime  even better utc  to avoid conflicts like overnight  daylight saving  different timezones between user and server etc  So I d recommend this approach  import datetime as dt   now   dt datetime now      or dt datetime now dt timezone utc   in 5 sec    now   dt timedelta seconds 5     get  14 39 57    in 5 sec strftime   H  M  S

User · Answer

Thanks to  Pax Diablo   bvmou and  Arachnid for the suggestion of using full datetimes throughout   If I have to accept datetime time objects from an external source  then this seems to be an alternative add secs to time   function   def add secs to time timeval  secs to add       dummy date   datetime date 1  1  1      full datetime   datetime datetime combine dummy date  timeval      added datetime   full datetime   datetime timedelta seconds secs to add      return added datetime time     This verbose code can be compressed to this one-liner    datetime datetime combine datetime date 1  1  1   timeval    datetime timedelta seconds secs to add   time     but I think I d want to wrap that up in a function for code clarity anyway

User · Answer

Try adding a datetime datetime to a datetime timedelta  If you only want the time portion  you can call the time   method on the resultant datetime datetime object to get it

User · Answer

Old question  but I figured I d throw in a function that handles timezones  The key parts are passing the datetime time object s tzinfo attribute into combine  and then using timetz   instead of time   on the resulting dummy datetime  This answer partly inspired by the other answers here   def add timedelta to time t  td          Add a timedelta object to a time object using a dummy datetime        param t  datetime time object       param td  datetime timedelta object        returns  datetime time object  representing the result of t   td       NOTE  Using a gigantic td may result in an overflow  You ve been     warned                Create a dummy date object      dummy date   date year 100  month 1  day 1         Combine the dummy date with the given time      dummy datetime   datetime combine date dummy date  time t  tzinfo t tzinfo         Add the timedelta to the dummy datetime      new datetime   dummy datetime   td        Return the resulting time  including timezone information      return new datetime timetz     And here s a really simple test case class  using built-in unittest    import unittest from datetime import datetime  timezone  timedelta  time  class AddTimedeltaToTimeTestCase unittest TestCase          Test add timedelta to time          def test wraps self           t   time hour 23  minute 59          td   timedelta minutes 2          t expected   time hour 0  minute 1          t actual   add timedelta to time t t  td td          self assertEqual t expected  t actual       def test tz self           t   time hour 4  minute 16  tzinfo timezone utc          td   timedelta hours 10  minutes 4          t expected   time hour 14  minute 20  tzinfo timezone utc          t actual   add timedelta to time t t  td td          self assertEqual t expected  t actual    if   name         main         unittest main

[python] What is the standard way to add N seconds to datetime.time in Python?

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