如何使用python更改分隔文件中的日期格式？

Question

我有一个以管道分隔的文本文件，其中记录如下：

ABC|1234|10/26/2016|PQRS|02/27/2016|

GHI|4321|02/27/2016|UOIP|10/26/2016|

正在寻找将mm/dd/yyyy格式更改为yyyy-mm-dd的方法

Answer 1

无需使用任何花招，只需使用str.split()作为：

>>> my_string = "ABC|1234|10/26/2016|PQRS|02/27/2016|"
>>> mm, dd, yy = my_string.split("|")[2].split("/")
>>> print "{}-{}-{}".format(yy, mm, dd)
2016-10-26

Answer 2

可能不是最干净的方法，但您可以尝试以下方法：

my_string = "ABC|1234|10/26/2016|PQRS|02/27/2016|"

#Split the string with the '|' character and return a list.
string_elements=my_string.split('|')

#The item 2 of the list (which is the first date) is split according to the '/' character
string_elements[2]=string_elements[2].split('/')
#The item 2 is transformed by making a rotation of the element to have the format yyyy-mm-dd and is joined on the character '-'    
string_elements[2]='-'.join(string_elements[2][-1:] + string_elements[2][:-1])

#Same as above for teh item 4 which is the second date
string_elements[4]=string_elements[4].split('/')
string_elements[4]='-'.join(string_elements[4][-1:] + string_elements[4][:-1])

#The list of item is joined with the '|' character to reform a string
my_transformed_string='|'.join(string_elements)
print my_transformed_string

结果是：

^{pr2}$

Answer 3

对来自datetime模块的strptime和strftime函数使用以下方法：

import datetime

# while iterating through the lines with a given format
# ...
line = 'ABC|1234|10/26/2016|PQRS|02/27/2016|'

line = '|'.join([item if k not in [2,4] else datetime.datetime.strptime(item, '%m/%d/%Y').strftime("%Y-%m-%d")
        for k, item in enumerate(line.split('|'))])

print(line)

输出（对于示例性线路）：

^{pr2}$

https://docs.python.org/3/library/datetime.html#strftime-and-strptime-behavior