Python получить дату начала месяца

Python Get First Day Of Month

When you work on a datetime in Python, you’ll likely need a way to find the first day of the month. Here’s a teachable Python lesson that walks through the steps to complete that coding task.

In this Python lesson, you’ll learn:

• How to get the first day of the month (start date)
• How to get the first day of next month and the previous month

Table of contents

How To Find The First Day Of The Month In Python

Let’s assume your application receives a datetime object, and you want to convert the given date to the first day of the month. For example, the datetime is ‘2022-9-14‘ and you want to write a code that will return you ‘2022-9-1‘, i.e., the first day of the month or the start date of a month.

The below steps show how to use the datetime.replace() method to find the first day of a month of a datetime object.

1. Import datetime class from a datetime modulePython datetime module provides various functions to create and manipulate the date and time. Use the from datetime import datetime statement to import a datetime class from a datetime module.
2. Store datetime object in a variable Store the input datetime object in a variable for further processing. Or you can use the datetime.today() to get the current datetime if you want to find the start date of a current month.
3. Use the datetime.replace() method The datetime.replace() function replaces the DateTime object’s contents with the given parameters. This method has various parameters, but here we will use the day parameter because we want to replace the day number of a datetime object with the 1 (first day of the month).

Example 1: Get the first day of the month using the replace() method

from datetime import datetime # get today's datetime input_dt = datetime.today() print('Datetime is:', input_dt) res = input_dt.replace(day=1) print('First day of a month:', res) # print only date print('Only date:', res.date())

Datetime is: 2022-09-15 15:43:55.304669 First day of a month: 2022-09-01 15:43:55.304669 Only date: 2022-09-01

Example 2: Get the first day of the month using the timedelta class

We can get the same result using the timedelta class of a datetime module.

A timedelta represents a duration which is the difference between two dates, time, or datetime instances, to the microsecond resolution. We can use the timedelta to add or subtract weeks, days, hours, minutes, seconds, microseconds, and milliseconds from a given DateTime.

Use the day parameter of a timedelta class to replace the day number of a datetime object with the 1 (first day of the month) to find the first day of the month using a specific date.

Use the below steps:

• First, import the datetime and timedelta class from a datetime module.
• Next, get the actual day number of an input datetime object using the strftime() method. For example, if datetime is ‘2022-8-24′, it will return ’24’.
• Next, use the timedelta class to subtract the actual day – 1 from an input date to get the first day of the month (starting date of a month)

from datetime import datetime, timedelta input_dt = datetime.today().date() print('Input date:', input_dt) # get the actual day number day_num = input_dt.strftime("%d") # subtract those number of days from input date # using the timedelta res = input_dt - timedelta(days=int(day_num) - 1) print('First day of month:', res)

Input date: 2022-09-15 First day of month: 2022-09-01

Get The First Day Of Next Month In Python

Let’s see how to get the first date of the next month in Python. For example, if datetime contains 2022-08-17, the first day of the next month is 2022-09-01. Also, if the datetime is ‘2021-12-31’, the first day of the next month is 2022-01-01.

Using the timedelta class from a DateTime module, we can get the first date of the next month.

Use the below steps.

• Import datetime and timedelta class from datetime module
• Replace the day number of a datetime to 1 using the datetime.replace() method
• Next, pick a number that certainly is more than any month but less than any two months combined and add them to input datetime using timedelta
• Next, again replace the day number of an input datetime to 1 using the datetime.replace() method

Example: Get The First Day Of Next Month

from datetime import datetime, timedelta input_dt = datetime(2022, 8, 26) print('Input date:', input_dt.date()) # first replace day number with 1 input_dt = input_dt.replace(day=1) # add 32 days to the input datetime input_dt = input_dt + timedelta(days=32) # replace day number with 1 res = input_dt.replace(day=1) print('First day of month:', res.date())

Input date: 2022-08-26 First day of month: 2022-09-01

The above solution works for all cases. See the below example.

from datetime import datetime, timedelta input_dt = datetime(2021, 12, 31) print((input_dt.replace(day=1) + timedelta(days=32)).replace(day=1)) input_dt = datetime(2020, 2, 29) print((input_dt.replace(day=1) + timedelta(days=32)).replace(day=1)) input_dt = datetime(2022, 12, 1) print((input_dt.replace(day=1) + timedelta(days=32)).replace(day=1))

2022-01-01 00:00:00 2020-03-01 00:00:00 2023-01-01 00:00:00

Get The First Day Of Previous Month In Python

Let’s see how to get the first date of the previous month in Python. For example, if datetime contains 2022-08-17, the first day of the previous month is 2022-07-01. Also, if the datetime is ‘2022-1-1’, the first day of the previous month is 2021-12-01.

Using the timedelta class from a DateTime module, we can get the first day of the previous month.

• Import datetime and timedelta class from datetime module
• Replace the day number of an input datetime to 1 using the datetime.replace(day=1) method
• Use timedelta to backup a single day to the last day of the previous month.
• Next, pick a number that certainly is more than any month but less than any two months combined and add them to input datetime using timedelta
• Next, again replace the day number of an input datetime to 1 using the datetime.replace(day=1) method

Example: Get The First Day Of the Previous Month

from datetime import datetime, timedelta input_dt = datetime(2021, 12, 31) print('Input datetime:', input_dt.date()) # first replace day number with 1 dt = input_dt.replace(day=1) # subtract 1 day from input datetime # go back to previous month i.e. last date of previous month dt = dt - timedelta(days=1) # replace day number with 1 res = dt.replace(day=1) print('first day of a previous month:', res.date())

Input datetime: 2021-12-31 first day of a previous month: 2021-11-01

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About Vishal

I’m Vishal Hule, Founder of PYnative.com. I am a Python developer, and I love to write articles to help students, developers, and learners. Follow me on Twitter

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найти первый день месяца в питоне

Я пытаюсь найти первый день месяца в python с одним условием: если моя текущая дата прошла 25 числа месяца, то первая переменная даты будет содержать первую дату следующего месяца вместо текущего месяца. Я делаю следующее:

import datetime todayDate = datetime.date.today() if (todayDate - todayDate.replace(day=1)).days > 25: x= todayDate + datetime.timedelta(30) x.replace(day=1) print x else: print todayDate.replace(day=1) 

Есть ли более чистый способ сделать это?

9 ответов

Это содержательное решение.

import datetime todayDate = datetime.date.today() if todayDate.day > 25: todayDate += datetime.timedelta(7) print todayDate.replace(day=1) 

В исходном примере кода нужно отметить одну вещь: использование timedelta(30) вызовет проблемы e, если вы тестируете последний день января. Вот почему я использую 7-дневную дельту.

In [1]: from dateutil.rrule import * In [2]: rrule(DAILY, bymonthday=1)[0].date() Out[2]: datetime.date(2018, 10, 1) In [3]: rrule(DAILY, bymonthday=1)[1].date() Out[3]: datetime.date(2018, 11, 1) 

Да, сначала установите дату и время начала текущего месяца.

Второй тест, если текущая дата дня> 25 и получить истинное / ложное на этом. Если True, то добавьте один месяц к объекту datetime начала месяца. Если false, используйте объект datetime со значением, установленным на начало месяца.

import datetime from dateutil.relativedelta import relativedelta todayDate = datetime.date.today() resultDate = todayDate.replace(day=1) if ((todayDate - resultDate).days > 25): resultDate = resultDate + relativedelta(months=1) print resultDate 

Модуль стрелка поможет вам избежать скрытых ошибок и использовать более старые продукты.

import arrow def cleanWay(oneDate): if currentDate.date().day > 25: return currentDate.replace(months=+1,day=1) else: return currentDate.replace(day=1) currentDate = arrow.get('25-Feb-2017', 'DD-MMM-YYYY') print (currentDate.format('DD-MMM-YYYY'), cleanWay(currentDate).format('DD-MMM-YYYY')) currentDate = arrow.get('28-Feb-2017', 'DD-MMM-YYYY') print (currentDate.format('DD-MMM-YYYY'), cleanWay(currentDate).format('DD-MMM-YYYY')) 

В этом случае вам не нужно, например, учитывать различную продолжительность месяцев. Вот вывод этого скрипта.

25-Feb-2017 01-Feb-2017 28-Feb-2017 01-Mar-2017 

Мое решение найти первый и последний день текущего месяца:

def find_current_month_last_day(today: datetime) -> datetime: if today.month == 2: return today.replace(day=28) if today.month in [4, 6, 9, 11]: return today.replace(day=30) return today.replace(day=31) def current_month_first_and_last_days() -> tuple: today = datetime.now().replace(hour=0, minute=0, second=0, microsecond=0) first_date = today.replace(day=1) last_date = find_current_month_last_day(today) return first_date, last_date 

from datetime import date from dateutil.relativedelta import relativedelta today = date.today() first_day = today.replace(day=1) if today.day > 25: print(first_day + relativedelta(months=1)) else: print(first_day) 

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Как получить первое число текущего месяца?

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