Get Last Day of the Month in Python

问题:

Is there a way using Python\'s standard library to easily determine (i.e. one function call) the last day of a given month?

If the standard library doesn\'t support that, does the dateutil package support this?

回答1:

I didn\'t notice this earlier when I was looking at the documentation for the calendar module, but a method called monthrange provides this information:

monthrange(year, month)
    Returns weekday of first day of the month and number of days in month, for the specified year and month.

>>> import calendar
>>> calendar.monthrange(2002,1)
(1, 31)
>>> calendar.monthrange(2008,2)
(4, 29)
>>> calendar.monthrange(2100,2)
(0, 28)

so:

calendar.monthrange(year, month)[1]

seems like the simplest way to go.

Just to be clear, monthrange supports leap years as well:

>>> from calendar import monthrange
>>> monthrange(2012, 2)
(2, 29)

My previous answer still works, but is clearly suboptimal.

回答2:

If you don\'t want to import the calendar module, a simple two-step function can also be:

import datetime

def last_day_of_month(any_day):
    next_month = any_day.replace(day=28) + datetime.timedelta(days=4)  # this will never fail
    return next_month - datetime.timedelta(days=next_month.day)

Outputs:

>>> for month in range(1, 13):
...     print last_day_of_month(datetime.date(2012, month, 1))
...
2012-01-31
2012-02-29
2012-03-31
2012-04-30
2012-05-31
2012-06-30
2012-07-31
2012-08-31
2012-09-30
2012-10-31
2012-11-30
2012-12-31

回答3:

EDIT: See @Blair Conrad\'s answer for a cleaner solution

---

>>> import datetime
>>> datetime.date (2000, 2, 1) - datetime.timedelta (days = 1)
datetime.date(2000, 1, 31)
>>> 

回答4:

EDIT: see my other answer. It has a better implementation than this one, which I leave here just in case someone\'s interested in seeing how one might \"roll your own\" calculator.

@John Millikin gives a good answer, with the added complication of calculating the first day of the next month.

The following isn\'t particularly elegant, but to figure out the last day of the month that any given date lives in, you could try:

def last_day_of_month(date):
    if date.month == 12:
        return date.replace(day=31)
    return date.replace(month=date.month+1, day=1) - datetime.timedelta(days=1)

>>> last_day_of_month(datetime.date(2002, 1, 17))
datetime.date(2002, 1, 31)
>>> last_day_of_month(datetime.date(2002, 12, 9))
datetime.date(2002, 12, 31)
>>> last_day_of_month(datetime.date(2008, 2, 14))
datetime.date(2008, 2, 29)

回答5:

This is actually pretty easy with dateutil.relativedelta (package python-datetutil for pip). day=31 will always always return the last day of the month.

Example:

from datetime import datetime
from dateutil.relativedelta import relativedelta

date_in_feb = datetime.datetime(2013, 2, 21)
print datetime.datetime(2013, 2, 21) + relativedelta(day=31)  # End-of-month
>>> datetime.datetime(2013, 2, 28, 0, 0)

回答6:

Using relativedelta you would get last date of month like this:

from dateutil.relativedelta import relativedelta
last_date_of_month = datetime(mydate.year,mydate.month,1)+relativedelta(months=1,days=-1)

The idea is to get the fist day of month and use relativedelta to go 1 month ahead and 1 day back so you would get the last day of the month you wanted.

回答7:

Another solution would be to do something like this:

from datetime import datetime

def last_day_of_month(year, month):
    \"\"\" Work out the last day of the month \"\"\"
    last_days = [31, 30, 29, 28, 27]
    for i in last_days:
        try:
            end = datetime(year, month, i)
        except ValueError:
            continue
        else:
            return end.date()
    return None

And use the function like this:

>>> 
>>> last_day_of_month(2008, 2)
datetime.date(2008, 2, 29)
>>> last_day_of_month(2009, 2)
datetime.date(2009, 2, 28)
>>> last_day_of_month(2008, 11)
datetime.date(2008, 11, 30)
>>> last_day_of_month(2008, 12)
datetime.date(2008, 12, 31)

回答8:

from datetime import timedelta
(any_day.replace(day=1) + timedelta(days=32)).replace(day=1) - timedelta(days=1)

回答9:

>>> import datetime
>>> import calendar
>>> date  = datetime.datetime.now()

>>> print date
2015-03-06 01:25:14.939574

>>> print date.replace(day = 1)
2015-03-01 01:25:14.939574

>>> print date.replace(day = calendar.monthrange(date.year, date.month)[1])
2015-03-31 01:25:14.939574

回答10:

if you are willing to use an external library, check out http://crsmithdev.com/arrow/

U can then get the last day of the month with:

import arrow
arrow.utcnow().ceil(\'month\').date()

This returns a date object which you can then do your manipulation.

回答11:

To get the last date of the month we do something like this:

from datetime import date, timedelta
import calendar
last_day = date.today().replace(day=calendar.monthrange(date.today().year, date.today().month)[1])

Now to explain what we are doing here we will break it into two parts:

first is getting the number of days of the current month for which we use monthrange which Blair Conrad has already mentioned his solution:

calendar.monthrange(date.today().year, date.today().month)[1]

second is getting the last date itself which we do with the help of replace e.g

>>> date.today()
datetime.date(2017, 1, 3)
>>> date.today().replace(day=31)
datetime.date(2017, 1, 31)

and when we combine them as mentioned on the top we get a dynamic solution.

回答12:

import datetime

now = datetime.datetime.now()
start_month = datetime.datetime(now.year, now.month, 1)
date_on_next_month = start_month + datetime.timedelta(35)
start_next_month = datetime.datetime(date_on_next_month.year, date_on_next_month.month, 1)
last_day_month = start_next_month - datetime.timedelta(1)

回答13:

For me it\'s the simplest way:

selected_date = date(some_year, some_month, some_day)

if selected_date.month == 12: # December
     last_day_selected_month = date(selected_date.year, selected_date.month, 31)
else:
     last_day_selected_month = date(selected_date.year, selected_date.month + 1, 1) - timedelta(days=1)

回答14:

The easiest way (without having to import calendar), is to get the first day of the next month, and then subtract a day from it.

import datetime as dt
from dateutil.relativedelta import relativedelta

thisDate = dt.datetime(2017, 11, 17)

last_day_of_the_month = dt.datetime(thisDate.year, (thisDate + relativedelta(months=1)).month, 1) - dt.timedelta(days=1)
print last_day_of_the_month

Output:

datetime.datetime(2017, 11, 30, 0, 0)

---

PS: This code runs faster as compared to the import calendarapproach; see below:

import datetime as dt
import calendar
from dateutil.relativedelta import relativedelta

someDates = [dt.datetime.today() - dt.timedelta(days=x) for x in range(0, 10000)]

start1 = dt.datetime.now()
for thisDate in someDates:
    lastDay = dt.datetime(thisDate.year, (thisDate + relativedelta(months=1)).month, 1) - dt.timedelta(days=1)

print (\'Time Spent= \', dt.datetime.now() - start1)


start2 = dt.datetime.now()
for thisDate in someDates:
    lastDay = dt.datetime(thisDate.year, 
                          thisDate.month, 
                          calendar.monthrange(thisDate.year, thisDate.month)[1])

print (\'Time Spent= \', dt.datetime.now() - start2)

OUTPUT:

Time Spent=  0:00:00.097814
Time Spent=  0:00:00.109791

This code assumes that you want the date of the last day of the month (i.e., not just the DD part, but the entire YYYYMMDD date)

回答15:

You can calculate the end date yourself. the simple logic is to subtract a day from the start_date of next month. :)

So write a custom method,

import datetime

def end_date_of_a_month(date):


    start_date_of_this_month = date.replace(day=1)

    month = start_date_of_this_month.month
    year = start_date_of_this_month.year
    if month == 12:
        month = 1
        year += 1
    else:
        month += 1
    next_month_start_date = start_date_of_this_month.replace(month=month, year=year)

    this_month_end_date = next_month_start_date - datetime.timedelta(days=1)
    return this_month_end_date

Calling,

end_date_of_a_month(datetime.datetime.now().date())

It will return the end date of this month. Pass any date to this function. returns you the end date of that month.

回答16:

This does not address the main question, but one nice trick to get the last weekday in a month is to use calendar.monthcalendar, which returns a matrix of dates, organized with Monday as the first column through Sunday as the last.

# Some random date.
some_date = datetime.date(2012, 5, 23)

# Get last weekday
last_weekday = np.asarray(calendar.monthcalendar(some_date.year, some_date.month))[:,0:-2].ravel().max()

print last_weekday
31

The whole [0:-2] thing is to shave off the weekend columns and throw them out. Dates that fall outside of the month are indicated by 0, so the max effectively ignores them.

The use of numpy.ravel is not strictly necessary, but I hate relying on the mere convention that numpy.ndarray.max will flatten the array if not told which axis to calculate over.

回答17:

Use pandas!

def isMonthEnd(date):
    return date + pd.offsets.MonthEnd(0) == date

isMonthEnd(datetime(1999, 12, 31))
True
isMonthEnd(pd.Timestamp(\'1999-12-31\'))
True
isMonthEnd(pd.Timestamp(1965, 1, 10))
False

回答18:

I prefer this way

import datetime
import calendar

date=datetime.datetime.now()
month_end_date=datetime.datetime(date.year,date.month,1) + datetime.timedelta(days=calendar.monthrange(date.year,date.month)[1] - 1)

回答19:

import calendar
from time import gmtime, strftime
calendar.monthrange(int(strftime(\"%Y\", gmtime())), int(strftime(\"%m\", gmtime())))[1]

Output:

31

This will print the last day of whatever the current month is. In this example it was 15th May, 2016. So your output may be different, however the output will be as many days that the current month is. Great if you want to check the last day of the month by running a daily cron job.

So:

import calendar
from time import gmtime, strftime
lastDay = calendar.monthrange(int(strftime(\"%Y\", gmtime())), int(strftime(\"%m\", gmtime())))[1]
today = strftime(\"%d\", gmtime())
lastDay == today

Output:

False

Unless it IS the last day of the month.

回答20:

If you want to make your own small function, this is a good starting point:

def eomday(year, month):
    \"\"\"returns the number of days in a given month\"\"\"
    days_per_month = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
    d = days_per_month[month - 1]
    if month == 2 and (year % 4 == 0 and year % 100 != 0 or year % 400 == 0):
        d = 29
    return d

For this you have to know the rules for the leap years:

• every fourth year
• with the exception of every 100 year
• but again every 400 years

回答21:

If you pass in a date range, you can use this:

def last_day_of_month(any_days):
    res = []
    for any_day in any_days:
        nday = any_day.days_in_month -any_day.day
        res.append(any_day + timedelta(days=nday))
    return res

回答22:

In the code below \'get_last_day_of_month(dt)\' will give you this, with date in string format like \'YYYY-MM-DD\'.

import datetime

def DateTime( d ):
    return datetime.datetime.strptime( d, \'%Y-%m-%d\').date()

def RelativeDate( start, num_days ):
    d = DateTime( start )
    return str( d + datetime.timedelta( days = num_days ) )

def get_first_day_of_month( dt ):
    return dt[:-2] + \'01\'

def get_last_day_of_month( dt ):
    fd = get_first_day_of_month( dt )
    fd_next_month = get_first_day_of_month( RelativeDate( fd, 31 ) )
    return RelativeDate( fd_next_month, -1 )

回答23:

Here is another answer. No extra packages required.

datetime.date(year + int(month/12), (month+1)%12, 1)-datetime.timdelta(days=1)

Get the first day of the next month and subtract a day from it.

回答24:

you can use relativedelta https://dateutil.readthedocs.io/en/stable/relativedelta.html month_end = <your datetime value within the month> + relativedelta(day=31) that will give you the last day.

回答25:

Here is a solution based python lambdas:

next_month = lambda y, m, d: (y, m + 1, 1) if m + 1 < 13 else ( y+1 , 1, 1)
month_end  = lambda dte: date( *next_month( *dte.timetuple()[:3] ) ) - timedelta(days=1)

The next_month lambda finds the tuple representation of the first day of the next month, and rolls over to the next year. The month_end lambda transforms a date (dte) to a tuple, applies next_month and creates a new date. Then the \"month\'s end\" is just the next month\'s first day minus timedelta(days=1).

回答26:

I hope,It\'s usefull for very much..Try it on this way..we must need import some package

import time
from datetime import datetime, date
from datetime import timedelta
from dateutil import relativedelta

  start_date = fields.Date(
        string=\'Start Date\', 
        required=True,
        ) 

    end_date = fields.Date(
        string=\'End Date\', 
        required=True,
        )

    _defaults = {
        \'start_date\': lambda *a: time.strftime(\'%Y-%m-01\'),
        \'end_date\': lambda *a: str(datetime.now() + relativedelta.relativedelta(months=+1, day=1, days=-1))[:10],
    }

回答27:

i have a simple solution:

import datetime   
datetime.date(2012,2, 1).replace(day=1,month=datetime.date(2012,2,1).month+1)-timedelta(days=1)
datetime.date(2012, 2, 29)