This is a brief introduction to date and time in Python.<\/p>\n
Here are some commonly used terms:<\/p>\n
The A Python datetime object can alo be created by parsing an ISO datetime string, or a string in a format of your choice<\/a>, according to C date and time formatting conventions:<\/p>\n The Python standard library has only limited ISO datetime string parsing features, and is not fully compatible with ISO 8601. Use third-party packages for full compatibility.<\/p>\n The timezone of your Here are some other useful methods you can call on your datetime object:<\/p>\n If you don\\’t need to deal with offsets and regions then Python lets you omit them, and create "naive" Naturally, the If you only need to deal with whole days then the Suppose you want to watch the final stage of Le Tour de France on Sunday 18th<\/sup> July 2021, sixteen days from today (at the time of writing), at 11:30 pm. You could calculate it as follows:<\/p>\n Line 3 creates a time difference object, a You can prove that two objects Zone unaware Similarly, be careful when obtaining the current moment. Don’t use If you use the PyTz<\/a> third party timezone library, don’t use a PyTz timezone object as an argument to the https:\/\/docs.python.org\/3\/library\/datetime.html<\/a><\/p>\n https:\/\/docs.python.org\/3\/library\/zoneinfo.html<\/a><\/p>\nzoneinfo<\/code> module uses your operating system\\’s time zone database if it is available, or the tzdata<\/code> Python package if it is unavailable. Create a new ZoneInfo<\/code> object as follows and use it to get the current timestamp or a datetime of your choosing:<\/p>\nfrom datetime import datetime\nfrom zoneinfo import ZoneInfo\n\nnow = datetime.now(ZoneInfo("Australia\/Sydney"))\n# Start date of Le Tour de France:\ntdf_start_date = datetime(2021,6,28,9,0,0,0,ZoneInfo("Europe\/Paris"))<\/code><\/pre>\n# End date of Le Tour de France, ISO style:\ntdf_end_date = datetime.fromisoformat("2021-07-18T18:00:00.000+02:00")\n# or in a custom format:\ntdf_end_date = datetime.strptime("18-07-2021 18:00:00.00 +0200", "%d-%m-%Y %H:%M:%S.%f %z")<\/code><\/pre>\nnow<\/code> object is stored in the tzinfo<\/code> attribute as shown: <\/p>\nnow.tzinfo\n# The utcoffset() method below returns a timedelta with a seconds attribute.\n# The next line prints 36000.\nnow.tzinfo.utcoffset(now).seconds<\/code><\/pre>\n# The weekday() method returns an integer number for the day of \n# the week, where Monday = 0.\nnow.weekday()\n# The isoformat() method returns a datetime string, \n# eg "2021-07-02T17:18:12.646789+10:00"\nnow.isoformat()\n# The dst() indicates whether daylight savings applies to \n# the datetime object. It returns a timedelta with a seconds \n# attribute, which is zero during standard time.\nnow.dst()<\/code><\/pre>\n"Naive" (Zone-Unaware) Date and Time<\/h3>\n
datetime<\/code> objects:<\/p>\nnow = datetime.now()<\/code><\/pre>\ntzinfo<\/code> attribute of such a datetime object will be None<\/code>:<\/p>\nprint(now.tzinfo)<\/code><\/pre>\nDate and Time<\/h3>\n
date<\/code><\/a> class is very handy. Similarly if you only need to deal with times, then Python provides the time<\/code><\/a> class.<\/p>\nfrom datetime import date, time, timezone\nfrom zoneinfo import ZoneInfo\ntoday = date.today()\ntdf_start_date = date(2021,6,28)\nnow_naive = time()\nnow_zoned = time(tzinfo=timezone.utc)\ntdf_start_time_naive = time(9,0,0,0)\ntdf_start_time_zoned = time(9,0,0,0,tzinfo=ZoneInfo("Europe\/Paris"))<\/code><\/pre>\nManipulating Dates and Times<\/h2>\n
from datetime import datetime, timedelta\nfrom zoneinfo import ZoneInfo\nsixteen_days = timedelta(days=16)\ntdf_final_sydney = datetime.now(ZoneInfo("Australia\/Sydney")) \\\n .replace(hour=23,minute=30,second=0) \\\n + sixteen_days\ntdf_final_paris = tdf_final_sydney.astimezone(ZoneInfo("Europe\/Paris"))<\/code><\/pre>\ntimedelta<\/code><\/a>. Different units of time can be supplied as named arguments, and these objects can be used to perform date and time arithmetic with datetime<\/code> objects and with other timedelta<\/code> objects. Line 4 gets today\\’s date in Sydney. Line 5 sets the time to 11:30 pm. Line 6 then uses the timedelta<\/code> to advance today\\’s date (Sydney time) sixteen days into the future, when the final will be. Line 7 calculates what time the start will be in Paris by adjusting the timezone, so you know what time it will be for the riders.<\/p>\ntdf_final_sydney<\/code> and tdf_final_paris<\/code>, which represent the start of the race in Sydney and Paris respectively, represent the same moment in time and have no time difference between them, by subtracting one from the other. Open a Python console and create the two variables with the code above, then run the code below:<\/p>\n>>> tdf_final_sydney - tdf_final_paris\ndatetime.timedelta(0)<\/code><\/pre>\nTraps and Pitfalls<\/h2>\n
datetime<\/code>s sometimes can produce wrong values in some versions of Python if you try to add zone information to them in the wrong way. eg:<\/p>\nfrom datetime import datetime, timezone\nbad_apr01 = datetime(2022,4,1).astimezone(timezone.utc) # WRONG!\napr01 = datetime(2022,4,1, tzinfo=timezone.utc) # CORRECT<\/code><\/pre>\nutcnow()<\/code> at all.<\/p>\nfrom datetime import datetime, timezone\nnow_wrong = datetime.utcnow() # WRONG! Is zone unaware!\nnow_correct = datetime.now(tz=timezone.utc) # CORRECT<\/code><\/pre>\ndatetime<\/code> constructor since it can give inconsistent results. There is more information about this on the package information page on PyPi but here is the short version:<\/p>\nimport pytz\nfrom datetime import datetime\nsydney_tz = pytz.timezone("Australia\/Sydney")\nbad_apr01 = datetime(2022,4,1 tzinfo=sydney_tz) # WRONG!\napr01 = sydney_tz.localize(datetime(2022,4,1)) # CORRECT<\/code><\/pre>\nFurther Reading<\/h2>\n