In Python how do you convert a datetime object to seconds

Question

Apologies for the simple question    I m new to Python    I have searched around and nothing seems to be working   I have a bunch of datetime objects and I want to calculate the number of seconds since a fixed time in the past for each one  for example since January 1  1970      import datetime t   datetime datetime 2009  10  21  0  0    This seems to be only differentiating between dates that have different days   t toordinal     Any help is much appreciated

User · Answer

To get the Unix time  seconds since January 1  1970     gt  gt  gt  import datetime  time  gt  gt  gt  t   datetime datetime 2011  10  21  0  0   gt  gt  gt  time mktime t timetuple    1319148000 0

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from the python docs   timedelta total seconds     Return the total number of seconds contained in the duration  Equivalent to   td microseconds    td seconds   td days   24   3600    10  6    10  6   computed with true division enabled   Note that for very large time intervals  greater than 270 years on most platforms  this method will lose microsecond accuracy   This functionality is new in version 2 7

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Maybe off-the-topic  to get UNIX POSIX time from datetime and convert it back    gt  gt  gt  import datetime  time  gt  gt  gt  dt   datetime datetime 2011  10  21  0  0   gt  gt  gt  s   time mktime dt timetuple     gt  gt  gt  s 1319148000 0    and back  gt  gt  gt  datetime datetime fromtimestamp s  datetime datetime 2011  10  21  0  0    Note that different timezones have impact on results  e g  my current TZ DST returns     gt  gt  gt   time mktime datetime datetime 1970  1  1  0  0  timetuple    -3600   -1h   therefore one should consider normalizing to UTC by using UTC versions of the functions   Note that previous result can be used to calculate UTC offset of your current timezone  In this example this is  1h  i e  UTC 0100    References     datetime date timetuple time mktime datetime datetime fromtimestamp introduction in time module explains POSIX time  1970 epoch  UTC  TZ  DST

User · Answer

The standard way to find the processing time in ms of a block of code in python 3 x is the following  import datetime  t start   datetime datetime now      Here is the python3 code  you want    to check the processing time of  t end   datetime datetime now   print  quot Time taken    quot    t end - t start  total seconds   1000   quot  ms quot

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int  t strftime   s    also works

User · Answer

Python provides operation on datetime to compute the difference between two date  In your case that would be  t - datetime datetime 1970 1 1   The value returned is a timedelta object from which you can use the member function total seconds to get the value in seconds   t - datetime datetime 1970 1 1   total seconds

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I tried the standard library s calendar timegm and it works quite well     convert a datetime to milliseconds since Epoch def datetime to utc milliseconds aDateTime       return int calendar timegm aDateTime timetuple    1000    Ref  https   docs python org 2 library calendar html calendar timegm

User · Answer

Starting from Python 3 3 this becomes super easy with the datetime timestamp   method  This of course will only be useful if you need the number of seconds from 1970-01-01 UTC    from datetime import datetime dt   datetime today      Get timezone naive now seconds   dt timestamp     The return value will be a float representing even fractions of a second  If the datetime is timezone naive  as in the example above   it will be assumed that the datetime object represents the local time  i e  It will be the number of seconds from current time at your location to 1970-01-01 UTC

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For the special date of January 1  1970 there are multiple options   For any other starting date you need to get the difference between the two dates in seconds  Subtracting two dates gives a timedelta object  which as of Python 2 7 has a total seconds   function    gt  gt  gt   t-datetime datetime 1970 1 1   total seconds   1256083200 0   The starting date is usually specified in UTC  so for proper results the datetime you feed into this formula should be in UTC as well  If your datetime isn t in UTC already  you ll need to convert it before you use it  or attach a tzinfo class that has the proper offset   As noted in the comments  if you have a tzinfo attached to your datetime then you ll need one on the starting date as well or the subtraction will fail  for the example above I would add tzinfo pytz utc if using Python 2 or tzinfo timezone utc if using Python 3

User · Answer

To convert a datetime object that represents time in UTC to POSIX timestamp   from datetime import timezone  seconds since epoch   utc time replace tzinfo timezone utc  timestamp     To convert a datetime object that represents time in the local timezone to POSIX timestamp   import tzlocal     pip install tzlocal  local timezone   tzlocal get localzone   seconds since epoch   local timezone localize local time  is dst None  timestamp     See How do I convert local time to UTC in Python  If the tz database is available on a given platform  a stdlib-only solution may work   Follow the links if you need solutions for  lt 3 3 Python versions

[python] In Python, how do you convert a `datetime` object to seconds?

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