Python method of calculating the first day of a month before and after a given point in time

An example of this article describes Python's method for calculating the 1st day of a month before and after a given point in time. To share for your reference, the details are as follows:

How to obtain the first month and the second month of the time point of python? Although there are many tutorials online, I feel it is too miscellaneous and not easy to use. After a study, I decided to provide a method and idea.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import datetime
import calendar
time = datetime.date(2017, 7, 20) # Year, month, day 
# For a month first 1 day 
first_day = datetime.date(time.year, time.month, 1)
print u' The first month 1 day :' + str(first_day)
# Ask before 1 In the first months 1 day 
# before 1 Months of the last 1 day 
pre_month = first_day - datetime.timedelta(days = 1) #timedelta is 1 It's a nice function 
print u' before 1 Months of the last 1 day :' + str(pre_month)
# before 1 In the first months 1 day 
first_day_of_pre_month = datetime.date(pre_month.year, pre_month.month, 1)
print u' before 1 In the first months 1 day :' + str(first_day_of_pre_month)
# After o 1 In the first months 1 day 
days_num = calendar.monthrange(first_day.year, first_day.month)[1] # To obtain 1 How many days are there in a month 
first_day_of_next_month = first_day + datetime.timedelta(days = days_num) # The end of the month 1 Day just days_num-1 Can be 
print u' after 1 In the first months 1 day :' + str(first_day_of_next_month)

The results are as follows

The 1st day of the month :2017-07-01
The last day of the previous month :2017-06-30
Day 1 of the previous month :2017-06-01
Day 1 of the following month :2017-08-01

PS: Here are a few more online tools for your reference:

Online days calculator:
http://tools.ofstack.com/jisuanqi/datejsq

In the day difference calculator:
http://tools.ofstack.com/jisuanqi/onlinedatejsq

Online date calculator/Difference day calculator:
http://tools.ofstack.com/jisuanqi/datecalc

Online Date/Day calculator:
http://tools.ofstack.com/jisuanqi/date_jisuanqi

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I hope this article has been helpful in Python programming.