Detailed explanation of Python datetime module, two practical classes of common time

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datetime is a commonly used time module in python,
which is used to obtain time and
convert between time types.
Two practical classes are introduced below.

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1. datetime.datetime class:

datetime.datetime.now()：Return the current time of the system (2018-09-18 18:39:55.921602)
datetime.datetime.now().date()：Returns the date at the current time (2018-09-18)
datetime.datetime.now().time()：Returns the hour, minute and second of the current time (18:40:24.946237)
datetime.datetime.ctime()：Convert datetime.datetime type to str type

testtime  = datetime.datetime.ctime(datetime.datetime.now())
print(type(testtime))
print(testtime)

#<class 'str'>
#Tue Sep 18 18:50:23 2018 python学习扣扣qun:540305994

Convert the time format to a string:

datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S'):
return time string (2018-11-09 14:42:36)

Convert string to time format

datetime.datetime.strptime('2018-11-09 14:42:36','%Y-%m-%d %H:%M:%S'):
Return datetime.datetime type time (2018-11-09 14:42:36)

Symbols representing date formatting

%y two-digit year representation (00-99)
%Y four-digit year representation (000-9999)
%m month (01-12)
%d day of month (0-31)
%H Hours in 24-hour format (0-23)
%I Hours in 12-hour format (01-12)
%M minutes (00=59)
%S seconds (00-59)
%a local abbreviated weekday name
%A local full weekday name
%b local abbreviated month name
%B local full month name
%c local corresponding date representation and time representation
%j day of the year (001-366)
%p equivalent of local AM or PM
%U week number of the year (00-53) Sunday is the beginning of the week
%w week (0-6), Sunday is the beginning of the week
%W week number of the year (00-53) Monday is the beginning of the week
%x local corresponding date representation
%X local corresponding time representation
%Z the name of the current time zone

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二、datetime.timedelta

datetime.timedelta

Used to calculate two datetime.datetime

Or the time difference between datetime.date types.

def __new__(cls, days=0, seconds=0, microseconds=0, 　　　milliseconds=0, minutes=0, hours=0, weeks=0):

From the constructor point of view,

Optional parameters :days、seconds、microseconds、milliseconds、minutes、hours、weeks，且默认是0。

This function can easily solve the calculation problem between time.
For example, if we want to know the date of today 300 days ago,
it can be implemented like this:

>>> now = datetime.datetime.now().date()
>>> now
datetime.date(2018, 11, 9)
>>> delta = datetime.timedelta(days = 300)
>>> now - delta
datetime.date(2018, 1, 13)
datetime.timedelta()也可以多个参数，比如计算300天12小时前的时间。


>>> now = datetime.datetime.now()
>>> now
datetime.datetime(2018, 11, 9, 15, 30, 36, 156323)
>>> delta = datetime.timedelta(days = 300,hours = 12)
>>> now - delta
datetime.datetime(2018, 1, 13, 3, 30, 36, 156323)

计算总天数和秒数。

>>> datetime.timedelta(days=1,hours = 2).days
1
>>> datetime.timedelta(days=1,hours = 2).total_seconds()
93600.0

That's it for today's article~

I am Cheese who loves to touch fish❤, see you in the next article (✿◡‿◡)

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