Python日期时间模块

在Python中，日期和时间不是它们自己的数据类型，但是可以导入一个名为datetime的模块来处理日期和时间。 Python Datetime 模块内置于Python中，因此无需在外部安装。

Python Datetime 模块提供了处理日期和时间的类。这些类提供了许多处理日期、时间和时间间隔的函数。 Date 和 datetime 是Python中的一个对象，因此当您操作它们时，您实际上是在操作对象，而不是字符串或时间戳。

DateTime 模块分为 6 个主要类 -

• date – 一个理想化的朴素日期，假设当前的公历一直有效，并且永远有效。它的属性是年、月和日。
• time – 一个理想化的时间，独立于任何特定的一天，假设每天正好有 24*60*60 秒。它的属性是小时、分钟、秒、微秒和tzinfo。
• datetime – 它是日期和时间以及属性年、月、日、小时、分钟、秒、微秒和 tzinfo 的组合。
• timedelta – 表示两个日期、时间或日期时间实例之间的差异的持续时间，以微秒为单位。
• tzinfo - 它提供时区信息对象。
• timezone – 将 tzinfo 抽象基类实现为与 UTC 的固定偏移量的类（3.2 版中的新功能）。

日期类

日期类用于在Python中实例化日期对象。实例化此类的对象时，它表示格式为 YYYY-MM-DD 的日期。此类的构造函数需要三个强制参数年、月和日期。

构造函数语法：

class datetime.date(year, month, day)

参数必须在以下范围内 -

• MINYEAR <= 年 <= MAXYEAR
• 1 <= 月 <= 12
• 1 <= 天 <= 给定月份和年份的天数

注意– 如果参数不是整数，则会引发 TypeError，如果超出范围，则会引发 ValueError。

示例 1：在Python中表示日期的 Date 对象

Python3

# Python program to
# demonstrate date class
 
# import the date class
from datetime import date
 
# initializing constructor
# and passing arguments in the
# format year, month, date
my_date = date(1996, 12, 11)
 
print("Date passed as argument is", my_date)
 
# Uncommenting my_date = date(1996, 12, 39)
# will raise an ValueError as it is
# outside range
 
# uncommenting my_date = date('1996', 12, 11)
# will raise a TypeError as a string is
# passed instead of integer

输出：

Date passed as argument is 1996-12-11

Traceback (most recent call last):
  File "/home/ccabfb570d9bd1dcd11dc4fe55fd6ba2.py", line 14, in 
    my_date = date(1996, 12, 39)
ValueError: day is out of range for month

Traceback (most recent call last):
  File "/home/53b974e10651f1853eee3c004b48c481.py", line 18, in 
    my_date = date('1996', 12, 11)
TypeError: an integer is required (got type str) 

示例 2：获取当前日期

使用日期类的今天（）函数返回当前本地日期。 today()函数带有几个属性（年、月和日）。这些可以单独打印。

Python3

# Python program to
# print current date
 
from datetime import date
 
# calling the today
# function of date class
today = date.today()
 
print("Today's date is", today)

输出

Today's date is 2021-08-19

示例 3：获取今天的年月日

我们可以使用日期类的年月日属性从日期对象中获取年月日属性。

Python3

from datetime import date
 
# date object of today's date
today = date.today()
 
print("Current year:", today.year)
print("Current month:", today.month)
print("Current day:", today.day)

输出

Current year: 2021
Current month: 8
Current day: 19

示例 4：从时间戳获取日期

我们可以使用 fromtimestamp() 方法从时间戳 y=创建日期对象。时间戳是从 1970 年 1 月 1 日 UTC 到特定日期的秒数。

Python3

from datetime import datetime
 
# Getting Datetime from timestamp
date_time = datetime.fromtimestamp(1887639468)
print("Datetime from timestamp:", date_time)

输出

Datetime from timestamp: 2029-10-25 16:17:48

示例 5：将日期转换为字符串

我们可以使用两个函数 isoformat() 和 strftime() 将日期对象转换为字符串表示。

Python3

from datetime import date
   
# calling the today
# function of date class
today = date.today()
   
# Converting the date to the string
Str = date.isoformat(today)
print("String Representation", Str)
print(type(Str))

输出

String Representation 2021-08-19

日期类方法列表

Function Name	Description
ctime()	Return a string representing the date
fromisocalendar()	Returns a date corresponding to the ISO calendar
fromisoformat()	Returns a date object from the string representation of the date
fromordinal()	Returns a date object from the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1
fromtimestamp()	Returns a date object from the POSIX timestamp
isocalendar()	Returns a tuple year, week, and weekday
isoformat()	Returns the string representation of the date
isoweekday()	Returns the day of the week as integer where Monday is 1 and Sunday is 7
replace()	Changes the value of the date object with the given parameter
strftime()	Returns a string representation of the date with the given format
timetuple()	Returns an object of type time.struct_time
today()	Returns the current local date
toordinal()	Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1
weekday()	Returns the day of the week as integer where Monday is 0 and Sunday is 6

时间班

时间类创建代表当地时间的时间对象，独立于任何一天。

构造函数语法：

class datetime.time(hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

所有参数都是可选的。 tzinfo 可以是 None 否则所有属性必须是以下范围内的整数 -

• 0 <= 小时 < 24
• 0 <= 分钟 < 60
• 0 <= 秒 < 60
• 0 <= 微秒 < 1000000
• 折叠 [0, 1]

示例 1：在Python中表示时间的时间对象

Python3

# Python program to
# demonstrate time class
 
from datetime import time
 
# calling the constructor
my_time = time(13, 24, 56)
 
print("Entered time", my_time)
 
# calling constructor with 1
# argument
my_time = time(minute=12)
print("\nTime with one argument", my_time)
 
# Calling constructor with
# 0 argument
my_time = time()
print("\nTime without argument", my_time)
 
# Uncommenting time(hour = 26)
# will rase an ValueError as
# it is out of range
 
# uncommenting time(hour ='23')
# will raise TypeError as
# string is passed instead of int

输出：

Entered time 13:24:56

Time with one argument 00:12:00

Time without argument 00:00:00

Traceback (most recent call last):
  File "/home/95ff83138a1b3e67731e57ec6dddef25.py", line 21, in 
    print(time(hour=26))
ValueError: hour must be in 0..23

Traceback (most recent call last):
  File "/home/fcee9ba5615b0b74fc3ba39ec9a789fd.py", line 21, in 
    print(time(hour='23'))
TypeError: an integer is required (got type str)

示例 2：获取小时、分钟、秒和微秒

创建时间对象后，也可以单独打印其属性。

Python3

from datetime import time
 
Time = time(11, 34, 56)
 
print("hour =", Time.hour)
print("minute =", Time.minute)
print("second =", Time.second)
print("microsecond =", Time.microsecond)

输出：

hour = 11
minute = 34
second = 56
microsecond = 0

示例 3：将 Time 对象转换为字符串

我们可以使用 isoformat() 方法将时间对象转换为字符串。

Python3

from datetime import time
 
# Creating Time object
Time = time(12,24,36,1212)
 
# Converting Time object to string
Str = Time.isoformat()
print("String Representation:", Str)
print(type(Str))

输出

String Representation: 12:24:36.001212

时间类方法列表

Function Name	Description
dst()	Returns tzinfo.dst() is tzinfo is not None
fromisoformat()	Returns a time object from the string representation of the time
isoformat()	Returns the string representation of time from the time object
replace()	Changes the value of the time object with the given parameter
strftime()	Returns a string representation of the time with the given format
tzname()	Returns tzinfo.tzname() is tzinfo is not None
utcoffset()	Returns tzinfo.utcffsets() is tzinfo is not None

日期时间类

DateTime 类包含有关日期和时间的信息。与日期对象一样，日期时间假定当前的公历在两个方向上扩展；与时间对象一样，datetime 假定每天正好有 3600*24 秒。

构造函数语法：

class datetime.datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0) 
 

年、月和日参数是强制性的。 tzinfo 可以是 None，其余所有属性必须是以下范围内的整数 -

• MINYEAR <= 年 <= MAXYEAR
• 1 <= 月 <= 12
• 1 <= 天 <= 给定月份和年份的天数
• 0 <= 小时 < 24
• 0 <= 分钟 < 60
• 0 <= 秒 < 60
• 0 <= 微秒 < 1000000
• 折叠 [0, 1]

注意– 传递整数以外的参数将引发 TypeError，传递超出范围的参数将引发 ValueError。

示例 1：在Python中表示 DateTime 的 DateTime 对象

Python3

# Python program to
# demonstrate datetime object
 
from datetime import datetime
 
# Initializing constructor
a = datetime(1999, 12, 12)
print(a)
 
# Initializing constructor
# with time parameters as well
a = datetime(1999, 12, 12, 12, 12, 12, 342380)
print(a)

输出：

1999-12-12 00:00:00
1999-12-12 12:12:12.342380

示例 2：获取年、月、小时、分钟和时间戳

创建 DateTime 对象后，也可以单独打印其属性。

Python3

from datetime import datetime
 
a = datetime(1999, 12, 12, 12, 12, 12)
 
print("year =", a.year)
print("month =", a.month)
print("hour =", a.hour)
print("minute =", a.minute)
print("timestamp =", a.timestamp())

输出：

year = 1999
month = 12
hour = 12
minute = 12
timestamp = 945000732.0

示例 3：当前日期和时间

您可以使用 Datetime.now()函数打印当前日期和时间。 now()函数返回当前的本地日期和时间。

Python3

from datetime import datetime
 
# Calling now() function
today = datetime.now()
 
print("Current date and time is", today)

输出：

Current date and time is 2019-10-25 11:12:11.289834

示例 4：将Python日期时间转换为字符串

我们可以使用 datetime.strftime 和 datetime.isoformat 方法在Python中将 Datetime 转换为字符串。

Python3

from datetime import datetime as dt
 
# Getting current date and time
now = dt.now()
 
string = dt.isoformat(now)
print(string)
print(type(string))

输出

2021-08-19T18:13:25.346259

日期时间类方法列表

Function Name	Description
astimezone()	Returns the DateTime object containing timezone information.
combine()	Combines the date and time objects and return a DateTime object
ctime()	Returns a string representation of date and time
date()	Return the Date class object
fromisoformat()	Returns a datetime object from the string representation of the date and time
fromordinal()	Returns a date object from the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1. The hour, minute, second, and microsecond are 0
fromtimestamp()	Return date and time from POSIX timestamp
isocalendar()	Returns a tuple year, week, and weekday
isoformat()	Return the string representation of date and time
isoweekday()	Returns the day of the week as integer where Monday is 1 and Sunday is 7
now()	Returns current local date and time with tz parameter
replace()	Changes the specific attributes of the DateTime object
strftime()	Returns a string representation of the DateTime object with the given format
strptime()	Returns a DateTime object corresponding to the date string
time()	Return the Time class object
timetuple()	Returns an object of type time.struct_time
timetz()	Return the Time class object
today()	Return local DateTime with tzinfo as None
toordinal()	Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1
tzname()	Returns the name of the timezone
utcfromtimestamp()	Return UTC from POSIX timestamp
utcoffset()	Returns the UTC offset
utcnow()	Return current UTC date and time
weekday()	Returns the day of the week as integer where Monday is 0 and Sunday is 6

时间增量类

Python timedelta 类用于计算日期差异，也可用于Python中的日期操作。这是执行日期操作的最简单方法之一。

构造函数语法：

class datetime.timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)
Returns : Date 

示例 1：向 datetime 对象添加天数

Python3

# Timedelta function demonstration
 
from datetime import datetime, timedelta
 
 
# Using current time
ini_time_for_now = datetime.now()
 
# printing initial_date
print("initial_date", str(ini_time_for_now))
 
# Calculating future dates
# for two years
future_date_after_2yrs = ini_time_for_now + timedelta(days=730)
 
future_date_after_2days = ini_time_for_now + timedelta(days=2)
 
# printing calculated future_dates
print('future_date_after_2yrs:', str(future_date_after_2yrs))
print('future_date_after_2days:', str(future_date_after_2days))

输出：

initial_date 2019-10-25 12:01:01.227848
future_date_after_2yrs: 2021-10-24 12:01:01.227848
future_date_after_2days: 2019-10-27 12:01:01.227848

示例 2：两个日期和时间之间的差异

使用此类也可以找到日期和时间差异。

Python3

# Timedelta function demonstration
from datetime import datetime, timedelta
 
# Using current time
ini_time_for_now = datetime.now()
 
# printing initial_date
print("initial_date", str(ini_time_for_now))
 
# Some another datetime
new_final_time = ini_time_for_now + \
    timedelta(days=2)
 
# printing new final_date
print("new_final_time", str(new_final_time))
 
 
# printing calculated past_dates
print('Time difference:', str(new_final_time -
                              ini_time_for_now))

输出：

initial_date 2019-10-25 12:02:32.799814
new_final_time 2019-10-27 12:02:32.799814
Time difference: 2 days, 0:00:00

Timedelta 类支持的操作

Operator	Description
Addition (+)	Adds and returns two timedelta objects
Subtraction (-)	Subtracts and returns two timedelta objects
Multiplication (*)	Multiplies timedelta object with float or int
Division (/)	Divides the timedelta object with float or int
Floor division (//)	Divides the timedelta object with float or int and return the int of floor value of the output
Modulo (%)	Divides two timedelta object and returns the remainder
+(timedelta)	Returns the same timedelta object
-(timedelta)	Returns the resultant of -1*timedelta
abs(timedelta)	Returns the +(timedelta) if timedelta.days > 1=0 else returns -(timedelta)
str(timedelta)	Returns a string in the form (+/-) day[s],  HH:MM:SS.UUUUUU
repr(timedelta)	Returns the string representation in the form of the constructor call

格式化日期时间

格式化日期时间可能非常必要，因为日期表示可能因地而异。就像在某些国家，它可以是 yyyy-mm-dd，而在其他国家，它可以是 dd-mm-yyyy。要格式化Python日期时间，可以使用 strptime 和 strftime 函数。

Python日期时间 strftime

strftime() 方法将给定的日期、时间或日期时间对象转换为给定格式的字符串表示形式。

示例： Python日期时间格式

Python3

# Python program to demonstrate
# strftime() function
 
 
from datetime import datetime as dt
 
# Getting current date and time
now = dt.now()
print("Without formatting", now)
 
# Example 1
s = now.strftime("%A %m %-Y")
print('\nExample 1:', s)
 
# Example 2
s = now.strftime("%a %-m %y")
print('\nExample 2:', s)
 
# Example 3
s = now.strftime("%-I %p %S")
print('\nExample 3:', s)
 
# Example 4
s = now.strftime("%H:%M:%S")
print('\nExample 4:', s)

输出

Without formatting 2021-08-19 18:16:25.881661

Example 1: Thursday 08 2021

Example 2: Thu 8 21

Example 3: 6 PM 25

Example 4: 18:16:25

注意：有关详细信息，请参阅 strftime() 方法。

Python日期时间 strptime

strptime() 从给定的字符串创建一个日期时间对象。

示例：日期时间 strptime

Python3

# import datetime module from datetime
from datetime import datetime
  
# consider the time stamps from a list  in string
# format DD/MM/YY H:M:S.micros
time_data = ["25/05/99 02:35:8.023", "26/05/99 12:45:0.003",
             "27/05/99 07:35:5.523", "28/05/99 05:15:55.523"]
  
# format the string in the given format : day/month/year 
# hours/minutes/seconds-micro seconds
format_data = "%d/%m/%y %H:%M:%S.%f"
  
# Using strptime with datetime we will format string
# into datetime
for i in time_data:
    print(datetime.strptime(i, format_data))

输出

1999-05-25 02:35:08.023000
1999-05-26 12:45:00.003000
1999-05-27 07:35:05.523000
1999-05-28 05:15:55.523000

处理Python DateTime 时区

DateTime 中的时区可用于可能希望根据特定区域的时区显示时间的情况。这可以使用Python的 pytz 模块来完成。该模块提供日期时间转换功能，并帮助用户服务于国际客户群。

Python3

from datetime import datetime
from pytz import timezone
 
format = "%Y-%m-%d %H:%M:%S %Z%z"
 
# Current time in UTC
now_utc = datetime.now(timezone('UTC'))
print(now_utc.strftime(format))
 
timezones = ['Asia/Kolkata', 'Europe/Kiev', 'America/New_York']
 
for tzone in timezones:
 
    # Convert to Asia/Kolkata time zone
    now_asia = now_utc.astimezone(timezone(tzone))
    print(now_asia.strftime(format))

输出

2021-08-19 18:27:28 UTC+0000
2021-08-19 23:57:28 IST+0530
2021-08-19 21:27:28 EEST+0300
2021-08-19 14:27:28 EDT-0400