time和datetime模块

Posted 2021-11-27

1.在Python中表示时间的方式

1.1时间戳

时间戳(timestamp)方式：通常来说，时间戳表示从1970年1月1日00:00:00开始按秒计算的偏移量。运行type(time.time())返回float类型
UTC （Coordinated Universal Time,世界协调时）即格林威治天文时间，世界标准时间。在中国为UTC+8。DST(Daylight Saving Time)即夏令时

>>> import time
>>> type(time.time())
<class ‘float‘>
>>> print(time.time())
1557046718.6016247

1.2.格式化的时间字符串

"2019-05-05"

1.3.元组

元组(struct_time)方式共九个元素。返回struct_time的函数主要有gmtime(),localtime(),strptime()。下面列出这种方式元组中的几个元素

索引（Index）    属性（Attribute）    值（Values）
0     tm_year（年）                             比如2011 
1     tm_mon（月）                             1 - 12
2     tm_mday（日）                           1 - 31
3     tm_hour（时）                             0 - 23
4     tm_min（分）                               0 - 59
5     tm_sec（秒）                               0 - 61
6     tm_wday（weekday）                  0 - 6（0表示周日）
7     tm_yday（一年中的第几天）        1 - 366
8     tm_isdst（是否是夏令时）            默认为-1

2.time模块的方法

• time.localtime([secs])：将一个时间戳转换为当前时区的struct_time。secs参数未提供，则以当前时间为准。

>>> time.localtime()
time.struct_time(tm_year=2019, tm_mon=5, tm_mday=5, tm_hour=17, tm_min=15, tm_sec=43, tm_wday=6, tm
_yday=125, tm_isdst=0)
>>> time.localtime()
time.struct_time(tm_year=2019, tm_mon=4, tm_mday=25, tm_hour=23, tm_min=57, tm_sec=32, tm_wday=3, tm_yday=115, tm_isdst=0)
>>> a.tm_year
2019
>>> ‘%s-%s-%s‘%(a.tm_year,a.tm_mon,a.tm_mday)
‘2019-4-26‘

• time.gmtime([secs])：和localtime()方法类似，gmtime()方法是将一个时间戳转换为UTC时区（0时区）的struct_time。0时区的时间+8小时是utc+8的时间

>>> time.gmtime()
time.struct_time(tm_year=2019, tm_mon=5, tm_mday=5, tm_hour=9, tm_min=20, tm_sec=41, tm_wday=6, tm_
yday=125, tm_isdst=0)

• time.time()：返回当前时间的时间戳。

>>> time.time()
1557048269.2991927

• time.mktime(t)：将一个struct_time转化为时间戳。

>>> time.mktime(time.localtime())
1557048434.0

• time.sleep(secs)：线程推迟指定的时间运行。单位为秒。

time.sleep(2)

• time.asctime([t])：把一个表示时间的元组或者struct_time表示为这种形式：‘Sun Oct 1 12:04:38 2017‘。如果没有参数，将会将time.localtime()作为参数传入。

>>> time.asctime(time.localtime())
‘Sun May  5 17:30:00 2019‘

• time.ctime([secs])：把一个时间戳（按秒计算的浮点数）转化为time.asctime()的形式。如果参数未给或者为None的时候，将会默认time.time()为参数。它的作用相当于time.asctime(time.localtime(secs))。

>>> time.ctime(time.time())
‘Sun May  5 17:34:26 2019‘

• time.strftime(format[, t])：把一个代表时间的元组或者struct_time（如由time.localtime()和time.gmtime()返回）转化为格式化的时间字符串。如果t未指定，将传入time.localtime()。

>>> time.strftime("%Y-%m-%d %X", time.localtime())
‘2019-05-05 17:37:35‘

• time.strptime(string[, format])：把一个格式化时间字符串转化为struct_time。实际上它和strftime()是逆操作。

>>> time.strptime(‘2019-05-05 17:37:35‘, "%Y-%m-%d %X")
time.struct_time(tm_year=2019, tm_mon=5, tm_mday=5, tm_hour=17, tm_min=37, tm_sec=35, tm_wday=6, tm
_yday=125, tm_isdst=-1)

字符串转时间格式对应表

    Meaning Notes
%a  Locale’s abbreviated weekday name.  
%A  Locale’s full weekday name. 
%b  Locale’s abbreviated month name.    
%B  Locale’s full month name.   
%c  Locale’s appropriate date and time representation.  
%d  Day of the month as a decimal number [01,31].   
%H  Hour (24-hour clock) as a decimal number [00,23].   
%I  Hour (12-hour clock) as a decimal number [01,12].   
%j  Day of the year as a decimal number [001,366].  
%m  Month as a decimal number [01,12].  
%M  Minute as a decimal number [00,59]. 
%p  Locale’s equivalent of either AM or PM. (1)
%S  Second as a decimal number [00,61]. (2)
%U  Week number of the year (Sunday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0.    (3)
%w  Weekday as a decimal number [0(Sunday),6].  
%W  Week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Monday are considered to be in week 0.    (3)
%x  Locale’s appropriate date representation.   
%X  Locale’s appropriate time representation.   
%y  Year without century as a decimal number [00,99].   
%Y  Year with century as a decimal number.  
%z  Time zone offset indicating a positive or negative time difference from UTC/GMT of the form +HHMM or -HHMM, where H represents decimal hour digits and M represents decimal minute digits [-23:59, +23:59]. 
%Z  Time zone name (no characters if no time zone exists).  
%%  A literal ‘%‘ character.

>>> time.strftime("%a",time.localtime())
‘Sun‘
>>> time.strftime("%A",time.localtime())
‘Sunday‘
>>> time.strftime("%b",time.localtime())
‘May‘
>>> time.strftime("%B",time.localtime())
‘May‘
>>> time.strftime("%c",time.localtime())
‘Sun May  5 17:54:45 2019‘
>>> time.strftime("%C",time.localtime())
‘20‘
>>> time.strftime("%d",time.localtime())
‘05‘
>>> time.strftime("%D",time.localtime())
‘05/05/19‘
>>> time.strftime("%H",time.localtime())
‘17‘
>>> time.strftime("%h",time.localtime())
‘May‘
>>> time.strftime("%I",time.localtime())
‘05‘
>>> time.strftime("%i",time.localtime())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Invalid format string
>>> time.strftime("%j",time.localtime())
‘125‘
>>> time.strftime("%m",time.localtime())
‘05‘
>>> time.strftime("%M",time.localtime())
‘57‘
>>> time.strftime("%p",time.localtime())
‘PM‘
>>> time.strftime("%S",time.localtime())
‘22‘
>>> time.strftime("%U",time.localtime())
‘18‘
>>> time.strftime("%W",time.localtime())
‘17‘
>>> time.strftime("%w",time.localtime())
‘0‘
>>> time.strftime("%x",time.localtime())
‘05/05/19‘
>>> time.strftime("%X",time.localtime())
‘17:58:54‘
>>> time.strftime("%y",time.localtime())
‘19‘
>>> time.strftime("%Y",time.localtime())
‘2019‘
>>> time.strftime("%Z",time.localtime())
‘?D1¨2?à¨o?á?¨o?à??‘
>>> time.strftime("%%",time.localtime())
‘%‘
>>>

3.datetime模块

datetime.date：表示日期的类。常用的属性有year, month, day；
datetime.time：表示时间的类。常用的属性有hour, minute, second, microsecond；
datetime.datetime：表示日期时间。
datetime.timedelta：表示时间间隔，即两个时间点之间的长度。
datetime.tzinfo：与时区有关的相关信息。（这里不详细充分讨论该类,可以参考python手册）

"需要记住的"
1.d=datetime.datetime.now() 返回当前的datetime日期类型
d.timestamp(),d.today(), d.year,d.timetuple()等方法可以调用

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: vita
import datetime
d = datetime.datetime.now()
print(d)
print("d.timestamp()",d.timestamp())
print("d.today()",d.today())
print("d.year",d.year)
print("d.timetuple()",d.timetuple())

E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
2019-05-05 18:11:52.005561
d.timestamp() 1557051112.005561
d.today() 2019-05-05 18:11:52.005561
d.year 2019
d.timetuple() time.struct_time(tm_year=2019, tm_mon=5, tm_mday=5, tm_hour=18, tm_min=11, tm_sec=52, tm_wday=6, tm_yday=125, tm_isdst=-1)

Process finished with exit code 0
2.datetime.date.fromtimestamp(时间戳)把时间戳转换为datetime日期类型
>>> datetime.date.fromtimestamp(1557051112.005561)
datetime.date(2019, 5, 5)
3.时间运算
>>> datetime.datetime.now()

datetime.datetime(2017, 10, 1, 12, 53, 11, 821218)

>>> datetime.datetime.now() + datetime.timedelta(4) #当前时间 +4天

datetime.datetime(2017, 10, 5, 12, 53, 35, 276589)

>>> datetime.datetime.now() + datetime.timedelta(hours=4) #当前时间+4小时

datetime.datetime(2017, 10, 1, 16, 53, 42, 876275)
4.时间替换
#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: vita
import datetime
d = datetime.datetime.now()

print(d.replace(year=2020,month=11,day=30))

print("d.timetuple()",d.timetuple())

E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
2020-11-30 18:16:59.517815
d.timetuple() time.struct_time(tm_year=2019, tm_mon=5, tm_mday=5, tm_hour=18, tm_min=16, tm_sec=59, tm_wday=6, tm_yday=125, tm_isdst=-1)

Process finished with exit code 0