Package: regta-period
regta-periodLibrary to make moment-independent periods in python.
It's designed especially forRegta Framework,
but with an ability to use it independently.Moment-Independence Idea ExplanationThis term in this context means that relying on this approach we can get the time to time
points regardless of the points in which we are.|-----------------|
        t1       t2     moment
--------|--------|--------|--------> time
                 |--------|Whereas with the standard intervals likedatetime.timedelta, we get an unnecessary offset:|-----------------|
        t1       t2     moment
--------|--------|--------|--------|--------> time
                 |-----------------|For example, it is important in the context of the job scheduler, because when the
scheduler is redeployed or restarted, you can get an unnecessary time shift or
unnecessary execution of the job.Math Explanation Of Moment-IndependenceRegular OffsetRegular offset is the same as python'stimedeltashift e.g. once per $n_1$ days,
$n_2$ hours, $n_3$ minutes, $n_4$ seconds, but with the moment-independence idea.Essentially, it works as a remainder of the time division from the Unix epoch.
Let $t_{unix}$ be the moment of the Unix epoch, a moment that we can get a grip on.
$t$ is the current moment. Then, the time since epoch is:$$\ \Delta t = t - t_{unix} $$Let $T$ be our regular period. Thus, to calculate time until the next moment we must subtract
from our period the remainder of the division by the period. Final function to calculate
time until the next moment since current looks following:$$\ f(t) = T - ( \Delta t \mod T ) = T - ( ( t - t_{unix} ) \mod T ) $$Time OffsetTime offset is stating the exact time e.g. at 9 pm, at 12 am, at 16:30, etc.
It works as a shift of the starting point in the exact time and time zone:$$\ t_{unix} + \Delta t_{time} + \Delta t_{tz} $$Note that it's not possible to combine exact time and short regular intervals such as
hours, minutes, and seconds.Time WindowsTime window is a static time frame in which the result should be included e.g. every Monday, every June, etc.
A window may be from $t_{min}$ to $t_{max}$, then function result must be included in this interval:$$ t + f(t) \in [t_{min}, t_{max}] $$If the expression above is true, it means that the result is included in the time window, and the result is correct.
If don't, we calculate the result from the maximum and calculate the next time window until we find a match:$$ t + f(t) \notin [t_{min_n}, t_{max_n}] \longrightarrow f(t_{max_n}); [t_{min_{n+1}}, t_{max_{n+1}}] $$InstallationInstall usingpip install regta-periodorpoetry add regta-periodIf you use python < 3.9, then also install backports:pip install "backports.zoneinfo[tzdata]"ExamplesThere are two ways to create periods: old school style and hipster style.fromdatetimeimportdatetimefromzoneinfoimportZoneInfofromregta_periodimportPeriod# Hipster stylep=Period().every(3).days.at("17:00").by("Europe/Moscow")# Old school stylep=Period(days=3,time="17:00",timezone=ZoneInfo("Europe/Moscow"))# <Period: regular_offset=259200.0s, time_offset=61200s, timezone=Europe/Moscow># Every 3 days at 5 pm by Moscow timet=datetime.now(tz=ZoneInfo("Europe/Moscow"))next_moment:datetime=p.get_next(t)# f(t) + tYou also may combine a few periods to a single object with the same interface:fromdatetimeimportdatetimefromregta_periodimportPeriod,PeriodAggregation,Weekdays# Hipster stylep=Period().on.weekdays.at("18:00")|Period().on.weekends.at("21:00")# You also may replace `|` with `.OR` to write shorter and more human-readable codep=Period().on.weekdays.at("18:00").OR.on.weekends.at("21:00")# Old school stylep=PeriodAggregation(Period(weekdays=[Weekdays.MONDAY,Weekdays.TUESDAY,Weekdays.WEDNESDAY,Weekdays.THURSDAY,Weekdays.FRIDAY],time="18:00",),Period(weekdays=[Weekdays.SATURDAY,Weekdays.SUNDAY],time="21:00",),)# All of the above will the same result:# <PeriodAggregation: <Period: regular_offset=86400.0s, time_offset=64800s, weekdays=Tuesday,Monday,Thursday,Wednesday,Friday> OR <Period: regular_offset=86400.0s, time_offset=75600s, weekdays=Sunday,Saturday>># At 6 pm on weekdays (Monday-Friday) and at 9 pm on weekends (Saturday-Sunday)t=datetime.now()timedelta_to_the_next_moment=p.get_interval(t)# f(t)Full documentation and reference are available atregta-period.alinsky.tech