从字符串创建Python日期时间

在本文中，我们将看到如何从给定的字符串创建一个Python DateTime 对象。

为此，我们将使用datetime.strptime()方法。 strptime() 方法返回一个 date_string 对应的 DateTime 对象，根据用户给出的格式字符串进行解析。

Syntax: datetime.strptime(date_string, format)

使用 strptime() 将字符串转换为日期时间

在这里，我们将一个简单的字符串转换为 datetime 对象，为此我们将字符串传递给 strptime() 并通过 this 对象化 datetime 对象。

Python3

from datetime import datetime
  
input_str = '21/01/24 11:04:19'
  
dt_object = datetime.strptime(
  input_str, '%d/%m/%y %H:%M:%S')
  
print("The type of the input date string now is: ", 
      type(dt_object))
  
print("The date is", dt_object)

输出：

The type of the input date string now is:  

The date is 2024-01-21 11:04:19

使用 strptime() 将包含单词的字符串转换为日期时间

strptime() 方法也允许您将“单词”中的时间戳转换为日期时间对象。下面的片段显示它可以完成：

蟒蛇3

from datetime import datetime
  
time_str = 'May 17 2019  11:33PM'
dt_object = datetime.strptime(
  time_str, '%b %d %Y %I:%M%p')
  
print(dt_object)

输出：

2019-05-17 23:33:00

Python strptime() 值错误

必须知道给定字符串的DateTime 格式，否则会导致不必要的问题和错误。下面的片段显示了可能导致的问题：

蟒蛇3

from datetime import datetime
  
time_str = '201123101455'
  
dt_obj = datetime.strptime(time_str, '%y%m%d%H%M%S')
dt_obj2 = datetime.strptime(time_str, '%d%m%y%H%S%M')
  
print ("1st interpretation of date from string is: ",dt_obj) 
print ("2nd interpretation of date from same string is", dt_obj2)

输出 ：

1st interpretation of date from string is:  2020-11-23 10:14:55

2nd interpretation of date from same string is 2023-11-20 10:55:14

如果字符串参数与格式参数不一致，则 strptime() 方法将不起作用。以下片段显示了由于格式说明符不匹配而发生的错误。

蟒蛇3

from datetime import datetime
  
time_str = '220917 114519'
dt_obj = datetime.strptime(time_str, '%d/%m/%y %H:%M:%S')
  
print ("The type is", type(dt_obj))
print ("The date is", date_time_obj)

输出：

ValueError(“time data %r does not match format %r” %(data_string, format))

格式代码列表

格式说明符大部分与 strftime() 方法相同。这些说明符是：

Directives	Meaning	Example
%a	Abbreviated weekday name.	Sun, Mon, …
%A	Full weekday name.	Sunday, Monday, …
%w	Weekday as a decimal number.	0, 1, …, 6
%d	Day of the month as a zero-padded decimal.	01, 02, …, 31
%-d	Day of the month as a decimal number.	1, 2, …, 30
%b	Abbreviated month name.	Jan, Feb, …, Dec
%B	Full month name.	January, February, …
%m	Month as a zero-padded decimal number.	01, 02, …, 12
%-m	Month as a decimal number.	1, 2, …, 12
%y	Year without century as a zero-padded decimal number.	00, 01, …, 99
%-y	Year without century as a decimal number.	0, 1, …, 99
%y	Year with century as a decimal number.	2013, 2019 etc.
%H	Hour (24-hour clock) as a zero-padded decimal number.	00, 01, …, 23
%-H	Hour (24-hour clock) as a decimal number.	0, 1, …, 23
%I	Hour (12-hour clock) as a zero-padded decimal number.	01, 02, …, 12
%-I	Hour (12-hour clock) as a decimal number.	1, 2, … 12
%p	Locale’s AM or PM.	AM, PM
%M	Minute as a zero-padded decimal number.	00, 01, …, 59
%-M	Minute as a decimal number.	0, 1, …, 59
%S	Second as a zero-padded decimal number.	00, 01, …, 59
%-S	Second as a decimal number.	0, 1, …, 59
%f	Microsecond as a decimal number, zero-padded on the left.	000000 – 999999
%z	UTC offset in the form +HHMM or -HHMM.
%Z	Time zone name.
%j	Day of the year as a zero-padded decimal number.	001, 002, …, 366
%-j	Day of the year as a decimal number.	1, 2, …, 366
%U	Week number of the year (Sunday as the first day of the week). All days in a new year preceding the first Sunday are considered to be in week 0.	00, 01, …, 53
%W	Week number of the year (Monday as the first day of the week). All days in a new year preceding the first Monday are considered to be in week 0.	00, 01, …, 53
%c	Locale’s appropriate date and time representation.	Mon Sep 30 07:06:05 2013
%x	Locale’s appropriate date representation.	09/30/13
%%	A literal ‘%’ character.	%