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dateutil.relativedelta - How to get duration in days?

I wish to get the total duration of a relativedelta in terms of days.
Expected:
dateutil.timedelta(1 month, 24 days) -> dateutil.timedelta(55 days)
What I tried:
dateutil.timedelta(1 month, 24 days).days -> 24 (WRONG)
Is there a simple way to do this? Thanks!

This one bothered me as well. There isn't a very clean way to get the span of time in a particular unit. This is partly because of the date-range dependency on units.
relativedelta() takes an argument for months. But when you think about how long a month is, the answer is "it depends". With that said, it's technically impossible to convert a relativedelta() directly to days, without knowing which days the delta lands on.
Here is what I ended up doing.
from datetime import datetime, timedelta
from dateutil.relativedelta import relativedelta
rd = relativedelta(years=3, months=7, days=19)
# I use 'now', but you may want to adjust your start and end range to a specific set of dates.
now = datetime.now()
# calculate the date difference from the relativedelta span
then = now - rd
# unlike normal timedelta 'then' is returned as a datetime
# subtracting two dates will give you a timedelta which contains the value you're looking for
diff = now - then
print diff.days

Simple date diff does it actually.
>>> from datetime import datetime
>>> (datetime(2017, 12, 1) - datetime(2018, 1, 1)).days
-31
To get positive number You can swap dates or use abs:
>>> abs((datetime(2017, 12, 1) - datetime(2018, 1, 1)).days)
31

In many situations you have a much restricted relativedelta, in my case, my relativedelta had only relative fields set (years, months, weeks, and days) and no other field. You may be able to get away with the simple method.
This is definitely off by few days, but it may be all you need
(365 * duration.years) + (30 * duration.months) + (duration.days)

Get date from week number

Please what's wrong with my code:
import datetime
d = "2013-W26"
r = datetime.datetime.strptime(d, "%Y-W%W")
print(r)
Display "2013-01-01 00:00:00", Thanks.

A week number is not enough to generate a date; you need a day of the week as well. Add a default:
import datetime
d = "2013-W26"
r = datetime.datetime.strptime(d + '-1', "%Y-W%W-%w")
print(r)
The -1 and -%w pattern tells the parser to pick the Monday in that week. This outputs:
2013-07-01 00:00:00
%W uses Monday as the first day of the week. While you can pick your own weekday, you may get unexpected results if you deviate from that.
See the strftime() and strptime() behaviour section in the documentation, footnote 4:
When used with the strptime() method, %U and %W are only used in calculations when the day of the week and the year are specified.
Note, if your week number is a ISO week date, you'll want to use %G-W%V-%u instead! Those directives require Python 3.6 or newer.

In Python 3.8 there is the handy datetime.date.fromisocalendar:
>>> from datetime import date
>>> date.fromisocalendar(2020, 1, 1) # (year, week, day of week)
datetime.date(2019, 12, 30, 0, 0)
In older Python versions (3.7-) the calculation can use the information from datetime.date.isocalendar to figure out the week ISO8601 compliant weeks:
from datetime import date, timedelta
def monday_of_calenderweek(year, week):
first = date(year, 1, 1)
base = 1 if first.isocalendar()[1] == 1 else 8
return first + timedelta(days=base - first.isocalendar()[2] + 7 * (week - 1))
Both works also with datetime.datetime.

To complete the other answers - if you are using ISO week numbers, this string is appropriate (to get the Monday of a given ISO week number):
import datetime
d = '2013-W26'
r = datetime.datetime.strptime(d + '-1', '%G-W%V-%u')
print(r)
%G, %V, %u are ISO equivalents of %Y, %W, %w, so this outputs:
2013-06-24 00:00:00
Availabe in Python 3.6+; from docs.

import datetime
res = datetime.datetime.strptime("2018 W30 w1", "%Y %W w%w")
print res
Adding of 1 as week day will yield exact current week start. Adding of timedelta(days=6) will gives you the week end.
datetime.datetime(2018, 7, 23)

If anyone is looking for a simple function that returns all working days (Mo-Fr) dates from a week number consider this (based on accepted answer)
import datetime
def weeknum_to_dates(weeknum):
return [datetime.datetime.strptime("2021-W"+ str(weeknum) + str(x), "%Y-W%W-%w").strftime('%d.%m.%Y') for x in range(-5,0)]
weeknum_to_dates(37)
Output:
['17.09.2021', '16.09.2021', '15.09.2021', '14.09.2021', '13.09.2021']

In case you have the yearly number of week, just add the number of weeks to the first day of the year.
>>> import datetime
>>> from dateutil.relativedelta import relativedelta
>>> week = 40
>>> year = 2019
>>> date = datetime.date(year,1,1)+relativedelta(weeks=+week)
>>> date
datetime.date(2019, 10, 8)

Another solution which worked for me that accepts series data as opposed to strptime only accepting single string values:
#fw_to_date
import datetime
import pandas as pd
# fw is input in format 'YYYY-WW'
# Add weekday number to string 1 = Monday
fw = fw + '-1'
# dt is output column
# Use %G-%V-%w if input is in ISO format
dt = pd.to_datetime(fw, format='%Y-%W-%w', errors='coerce')

Here's a handy function including the issue with zero-week.

Date 6 months into the future

I am using the datetime Python module in django. I am looking to calculate the date if the expiry date is less than or equal to 6 months from the current date.
The reason I want to generate a date 6 months from the current date is to set an alert that will highlight the field/column in which that event occurs. I dont know if my question is clear. I have been reading about timedelta function but cant really get my head round it. I am trying to write an if statement to statisfy this condition. Anyone able to help me please? Am a newbie to django and python.

There are two approaches, one only slightly inaccurate, one inaccurate in a different way:
Add a datetime.timedelta() of 365.25 / 2 days (average year length divided by two):
import datetime
sixmonths = datetime.datetime.now() + datetime.timedelta(days=365.25/2)
This method will give you a datetime stamp 6 months into the future, where we define 6 monhs as exactly half a year (on average).
Use the external dateutil library, it has a excellent relativedelta class that will add 6 months based on calendar calculations to your current date:
import datetime
from dateutil.relativedelat import relativedelta
sixmonths = datetime.datetime.now() + relativedelta(months=6)
This method will give you a datetime stamp 6 months into the future, where the month component of the date has been forwarded by 6, and it'll take into account month boundaries, making sure not to cross them. August 30th plus 6 months becomes February 28th or 29th (leap years permitting), for example.
A demonstration could be helpful. In my timezone, at the time of posting, this translates to:
>>> import datetime
>>> from dateutil.relativedelta import relativedelta
>>> now = datetime.datetime.now()
>>> now
datetime.datetime(2013, 2, 18, 12, 16, 0, 547567)
>>> now + datetime.timedelta(days=365.25/2)
datetime.datetime(2013, 8, 20, 3, 16, 0, 547567)
>>> now + relativedelta(months=6)
datetime.datetime(2013, 8, 18, 12, 16, 0, 547567)
So there is a 1 day and 15 hour difference between the two methods.
The same methods work fine with datetime.date objects too:
>>> today = datetime.date.today()
>>> today
datetime.date(2013, 2, 18)
>>> today + datetime.timedelta(days=365.25/2)
datetime.date(2013, 8, 19)
>>> today + relativedelta(months=6)
datetime.date(2013, 8, 18)
The half-year timedelta becomes a teensy less accurate when applied to dates only (the 5/8th day component of the delta is ignored now).

If by "6 months" you mean 180 days, you can use:
import datetime
d = datetime.date.today()
d + datetime.timedelta(6 * 30)
Alternatively if you, mean actual 6 months by calendar you'll have to lookup the calendar module and do some lookups on each month. For example:
import datetime
import calendar
def add_6_months(a_date):
month = a_date.month - 1 + 6
year = a_date.year + month / 12
month = month % 12 + 1
day = min(a_date.day,calendar.monthrange(year, month)[1])
return datetime.date(year, month, day)

I would give Delorean a look a serious look. It is built on top of dateutil and pytz to do what you asked would simply be the following.
>>> d = Delorean()
>>> d
Delorean(datetime=2013-02-21 06:00:21.195025+00:00, timezone=UTC)
>>> d.next_month(6)
Delorean(datetime=2013-08-21 06:00:21.195025+00:00, timezone=UTC)
It takes into account all the dateutil calculations as well as provide and interface for timezone shifts. to get the needed datetime simple .datetime on the Delorean object.

this might work for you in case you want to get an specfic date back:
from calendar import datetime
datetime.date(2019,1,1).strftime("%a %d")
#The arguments here are: year, month, day and the method is there to return a formated kind of date - in this case - day of the week and day of the month.
The outcome would be:
Tue 01
Hope it helps!

Converting date formats python - Unusual date formats - Extract %Y%M%D

I have a large data set with a variety of Date information in the following formats:
DAYS since Jan 1, 1900 - ex: 41213 - I believe these are from Excel http://www.kirix.com/stratablog/jd-edwards-date-conversions-cyyddd
YYDayofyear - ex 2012265
I am familiar with python's time module, strptime() method, and strftime () method. However, I am not sure what these date formats above are called on if there is a python module I can use to convert these unusual date formats.
Any idea how to get the %Y%M%D format from these unusual date formats without writing my own calculator?
Thanks.

You can try something like the following:
In [1]: import datetime
In [2]: s = '2012265'
In [3]: datetime.datetime.strptime(s, '%Y%j')
Out[3]: datetime.datetime(2012, 9, 21, 0, 0)
In [4]: d = '41213'
In [5]: datetime.date(1900, 1, 1) + datetime.timedelta(int(d))
Out[5]: datetime.date(2012, 11, 2)
The first one is the trickier one, but it uses the %j parameter to interpret the day of the year you provide (after a four-digit year, represented by %Y). The second one is simply the number of days since January 1, 1900.
This is the general conversion - not sure of your input format but hopefully this can be tweaked to suit it.

On the Excel integer to Python datetime bit:
Note that there are two Excel date systems (one 1-Jan-1900 based and another 1-Jan 1904 based); see https://support.microsoft.com/en-us/help/214330/differences-between-the-1900-and-the-1904-date-system-in-excel for more information.
Also note that the system is NOT zero-based. So, in the 1900 system, 1-Jan-1900 is day 1 (not day 0).
import datetime
EXCEL_DATE_SYSTEM_PC=1900
EXCEL_DATE_SYSTEM_MAC=1904
i = 42129 # Excel number for 5-May-2015
d = datetime.date(EXCEL_DATE_SYSTEM_PC, 1, 1) + datetime.timedelta(i-2)

Both of these formats seems pretty straightforward to work with. The first one, in fact, is just an integer, so why don't you just do something like this?
import datetime
def days_since_jan_1_1900_to_datetime(d):
return datetime.datetime(1900,1,1) + \
datetime.timedelta(days=d)
For the second one, the details depend on exactly how the format is defined (e.g. can you always expect 3 digits after the year even when the number of days is less than 100, or is it possible that there are 2 or 1 – and if so, is the year always 4 digits?) but once you've got that part down it can be done very similarly.

According to http://docs.python.org/2/library/datetime.html#strftime-and-strptime-behavior
, day of the year is "%j", whereas the first case can be solved by toordinal() and fromordinal(): date.fromordinal(date(1900, 1, 1).toordinal() + x)

I'd think timedelta.
import datetime
d = datetime.timedelta(days=41213)
start = datetime.datetime(year=1900, month=1, day=1)
the_date = start + d
For the second one, you can 2012265[:4] to get the year and use the same method.
edit: See the answer with %j for the second.

from datetime import datetime
df(['timeelapsed'])=(pd.to_datetime(df['timeelapsed'], format='%H:%M:%S') - datetime(1900, 1, 1)).dt.total_seconds()

How to convert Year and Day of Year to Date?

I have a year value and a day of year and would like to convert to a date (day/month/year).

datetime.datetime(year, 1, 1) + datetime.timedelta(days - 1)

>>> import datetime
>>> datetime.datetime.strptime('2010 120', '%Y %j')
datetime.datetime(2010, 4, 30, 0, 0)
>>> _.strftime('%d/%m/%Y')
'30/04/2010'

The toordinal() and fromordinal() functions of the date class could be used:
from datetime import date
date.fromordinal(date(year, 1, 1).toordinal() + days - 1)

since it is pretty common these days, a pandas option, using pd.to_datetime with specified unit and origin:
import pandas as pd
day, year = 21, 2021
print(pd.to_datetime(day-1, unit='D', origin=str(year)))
# 2021-01-21 00:00:00

>>>import datetime
>>>year = int(input())
>>>month = int(input())
>>>day = int(input())
data = datetime.datetime(year,month,day)
daynew = data.toordinal()
yearstart = datetime.datetime(year,1,1)
day_yearstart = yearstart.toordinal()
print ((daynew-day_yearstart)+1)

Using the mx.DateTime module to get the date is similar to what has been proposed above using datetime and timedelta. Namely:
import mx.DateTime as dt
date = dt.DateTime(yyyy,mm,dd) + dt.DateTimeDeltaFromDays(doy-1)
So, given that you know the year (say, 2020) and the doy (day of the year, say 234), then:
date = dt.DateTime(2020,1,1) + dt.DateTimeFromDays(233)
which returns
2020-08-21 00:00:00.00
The advantage of the mx.DateTime library is that has many useful features. As per description in its homepage:
Parses date/time string values in an almost seamless way.
Provides conversion routines to and from many different alternative date/time
storage formats.
Includes an easy-to-use C API which makes
integration a breeze.
Fast, memory efficient, accurate.
Georgian and Julian calendar support.
Vast range of valid dates (including B.C. dates).
Stable, robust and portable (mxDateTime has been around for almost 15 years
now).
Fully interoperates with Python's time and datetime modules.