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In this video, we delve into the concept of `timedelta` objects, which represent durations or intervals between dates or datetimes. Learn the syntax for creating `timedelta` objects and explore their optional arguments, which default to zero. Understand how timedelta` objects store time intervals and grasp their practical use in calculating time differences, setting alarms, and working with date and time intervals.
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Dates, times and date times,
are very tangible concepts.
0:00
Now to something more abstract,
the time delta object.
0:06
The time delta object
represents a duration,
0:11
the difference or the interval
between two dates or date times.
0:15
The constructor syntax for
a time delta object looks like this.
0:21
Datetime.timedelta, microseconds,
milliseconds,
0:25
seconds, minutes, hours, days, and weeks.
0:30
Now microseconds and milliseconds are
rarely used, so we'll omit those for now.
0:36
Still, there are a lot of
arguments left here, but
0:42
luckily they're all optional and
they all default to zero.
0:46
When we create a time delta object,
we create a time difference or interval.
0:52
So zero is a valid value,
even for days and weeks.
0:58
Because you can have zero
days between two times.
1:03
Something more important to
remember is that even though we can
1:07
input all of these types of time
intervals into a time delta,
1:13
only days, seconds and
microseconds are stored in the object.
1:17
If we put 1 hour,
23 minutes into the timedelta constructor,
1:23
it'll actually store 60 minutes plus 23
minutes times 60 to get the seconds value.
1:27
Similarly, if we put 2 weeks
into the timedelta constructor,
1:36
It'll actually store 14 days instead.
1:41
On the flip side, if we put 100,000
seconds into the timedelta constructor,
1:45
this will actually store as 1 day and
13600 seconds.
1:53
One way of using the timedelta
object is to find or
1:58
create a new date, time or
date time relative to an existing one.
2:03
Let me explain.
2:10
Let's say we've got an app
that sets alarms and
2:12
we want to set an alarm for
one hour and 30 minutes.
2:15
The app will need to know what time it
is now and what time to sound the alarm.
2:20
Time delta is used in this case to
store the difference between now and
2:26
the alarm going off,
which is one hour and 30 minutes.
2:31
So let's create the time
delta object first.
2:36
Alarm equals datetime.timedelta
2:40
Hours equals 1, minutes equals 30.
2:44
Now let's see when this
alarm should go off.
2:48
Alarm plus datetime.datetime.now.
2:53
And there we have it.
3:01
That's the time that
the alarm should go off.
3:02
We've just added 1 hour and 30 minutes
to the time now by using time delta.
3:05
Let's try an example with dates.
3:12
I want to run a report for
the last 72 days, but
3:14
I'm not sure when
the start date should be.
3:18
Instead of counting backwards
while looking at a calendar,
3:21
let's use time delta.
3:26
Let's first create the time
delta report equals
3:28
datetime.timedelta(days=72).
3:33
And now we want to work backwards in time.
3:37
So instead of adding the time delta
to a date object will subtract.
3:41
So datetime.date.today minus report,
which is 72 days,
3:45
to give us the date that we
need to run this report from.
3:51
Here we've subtracted
72 days from today to
3:57
find the start date of our
report by using time delta.
4:00
Another use of time delta is to work out
the difference between two dates or times.
4:07
Let's find out how long
I've been working today?
4:13
First let's create a date time object for
when I started working today.
4:16
So started_work equals
datetime.datetime
4:21
2023, 9, 4 and 7am.
4:28
Then let's subtract that from the time
now to get a time delta that tells
4:34
us how long I've been working for.
4:39
Time_worked equals datetime.datetime.now
minus started_work.
4:41
Let's check it out with time_worked.
4:51
Looks like I've been working for
16,123 seconds.
4:55
We can do some simple math to get
the hours and minutes that I've worked.
5:02
So we can do time_worked.seconds/60
to see how many minutes,
5:07
or time worked.seconds/60/60
5:15
again to see how many hours, pretty cool.
5:20
Let's give it another go and
find the difference between two birthdays.
5:25
I'm going to create a variable for
my birthday.
5:32
Me equals datetime.date 1993,
5:34
12, 11 and another variable to
5:39
store my cat Rubik's birthday,
5:44
rubik = datetime.date(2022, 9, 27).
5:49
Then I'm simply going to subtract
my birthday from Rubiks birthday
5:57
to see our age difference.
6:01
Now here I'm subtracting my birthday from
Rubiks birthday because his birthday is
6:03
the more recent date.
6:07
Wow.
6:10
10,517 days that's a lot of days.
6:11
Now, you'll notice that the time delta
returned only the days argument.
6:17
As mentioned before, a time delta
object actually only stores the day,
6:22
seconds, and microseconds properties.
6:26
But what if I want to know how many years,
months, and days exactly.
6:30
Now we could do some
math to figure that out.
6:35
We can divide that big number by 365 to
find the number of years and then divide
6:38
the remainder in two months, and then
the remainder of that will be our days.
6:43
But what about leap years?
6:49
And what about the different number
of days for different months?
6:51
Right now,
all we have is a number of days.
6:55
Without the context of the whole calendar,
we aren't actually able to
6:59
work out the years, months, and
days between me and Rubik's birthdays.
7:03
So let's make use of
a third-party module that will
7:08
make date-time calculations
much more accessible.
7:12
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