Summary of Python time acquisition and conversion knowledge

Time processing is the most common requirement in our daily development, such as: getting the current datetime, getting today's date, getting tomorrow/previous N days, getting the start and end time of the day (00:00:00 23:59:59 ), get the time difference between two datetimes, get the last day of this week/this month/last month, etc. These conversions seem messy and difficult to remember, so today we will summarize Python’s time processing.

Principle: Take datetime as the center, starting point or transit, and convert it into the target object, covering the date conversion processing required in most business scenarios

Steps:

1. Master several objects and their relationships

2. Understand the basic operation methods of each type of object

3. Convert through transformation relationships

datetime is date A combination with time, including all information about date and time.

The function prototype is:

datetime. datetime (year, month, day[ , hour[ , minute[ , second[ , microsecond[ , tzinfo] ] ] ] ] )
The meaning of each parameter is the same as that in the date and time constructors. Pay attention to the range of parameter values.

Example:

1. Get the datetime object

The code is as follows:

import datetime
now = datetime.datetime.now()
#输出：datetime.datetime(2016, 11, 26, 8, 34, 30, 876359)

2.Get the timestamp(timestamp)

Time The stamp is the number of seconds since January 1, 1970 (00:00:00 GMT). It is also called Unix Timestamp.

The code is as follows:

import time
time.time()
#输出：1480120686.733905

3. Get time tuple (tuple)

The code is as follows:

import time
time.localtime()
#输出：time.struct_time(tm_year=2016, tm_mon=11, tm_mday=26, tm_hour=8, tm_min=39, tm_sec=33, tm_wday=5, tm_yday=331, tm_isdst=0)

4. Get time string (string)

String format parameter list:
datetime. strftime (format)
%a: Abbreviation of week. For example, Wednesday is Web
%A: The full letter of the week. For example, Wednesday is Wednesday
%b: the abbreviation of the month. For example, April is Apr
%B: the full month. For example, the month of April is April
%c: string representation of date and time. (For example: 04/07/10 10:43:39)
%d: The number of days in this month (the number of days in this month)
%f: Microseconds (range [0,999999 ])
%H: Hour (24-hour format, [0, 23])
%I: Hour (12-hour format, [0, 11])
%j: The number of days in the year [001,366] (the day of the year)
%m: month ([01,12])
%M: minute ([00,59])
%p: AM or PM
%S: Seconds (range is [00, 61], why not [00, 59], refer to the python manual~_~)
%U: The number of weeks in the year and the week in the year), Sunday as The first day of the week
%w: The number of days today is in this week, the range is [0, 6], 6 means Sunday
%W: The number of weeks in the year (the first week of the year), Monday is the first day of the week
%x: date string (such as: 04/07/10)
%X: time string (such as: 10:43:39)
%y: Year represented by 2 digits
%Y: Year represented by 4 digits
%z: Interval with UTC time (if it is local time, return an empty string)
%Z: Time zone name (if is the local time, returns an empty string)
%%: %% => %

The code is as follows:

import datetime
datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
'2016-11-26 08:40:39'

5.date (date)

Code As follows:

import datetime
datetime.datetime.now().date()
datetime.date(2016, 11, 26)

6. Get today’s date

The code is as follows:

import datetime
datetime.date.today()
datetime.date(2016, 11, 26)

7. Get tomorrow/previous N days

Tomorrow

The code is as follows:

import datetime
datetime.date.today() + datetime.timedelta(days=1)
datetime.date(2016, 11, 27)

Two days ago

The code is as follows:

import datetime
>>> datetime.datetime.now()
datetime.datetime(2016, 11, 26, 8, 42, 59, 665368)
>>> datetime.datetime.now() - datetime.timedelta(days=3)
datetime.datetime(2016, 11, 24, 8, 43, 14, 696948)

8. Get the start and end time of the day (00:00:00 23:59:59)

The code is as follows:

import datetime
datetime.datetime.combine(datetime.date.today(), datetime.time.min)
datetime.datetime(2016, 11, 26, 0, 0)
datetime.datetime.combine(datetime.date.today(), datetime.time.max)
datetime.datetime(2016, 11, 26, 23, 59, 59, 999999)

9. Get the time difference between two datetimes

The code is as follows:

import datetime
(datetime.datetime(2016,12,13,12,0,0) - datetime.datetime.now()).total_seconds()
1480506.809658

10. Get the last day of this week/this month/last month

This week

The code is as follows:

import datetime
today = datetime.date.today()
#输出： datetime.date(2016, 11, 26)
sunday = today + datetime.timedelta(6 - today.weekday())
#输出：datetime.date(2016, 11, 27)

This month

The code is as follows:

import calendar
today = datetime.date.today()
last_day_num = calendar.monthrange(today.year, today.month)
last_day = datetime.date(today.year, today.month, last_day_num)
#输出：datetime.date(2016, 11, 30)

11. Get the last day of the previous month (may span New Years )

The code is as follows:

import datetime
today = datetime.date.today()
first = datetime.date(day=1, month=today.month, year=today.year)
lastMonth = first - datetime.timedelta(days=1)
#输出：datetime.date(2016, 10, 31)

Other usage examples:

The code is as follows:

#当月1号
datetime.date(datetime.date.today().year,datetime.date.today().month,1)
#当月1号
datetime.date.today().replace(day=1)
#上月1号
(datetime.date.today().replace(day=1) - datetime.timedelta(1)).replace(day=1)

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