从 Python 中的日期减去 n 天
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Subtracting n days from date in Python
提问by Isak
I want to subtract n days from a file's timestamp, but it doesn't seem to be working. I have read this post, and I think I'm close.
我想从文件的时间戳中减去 n 天，但它似乎不起作用。我已经阅读了这篇文章，我想我已经接近了。
This is an excerpt from my code:
这是我的代码的摘录：
import os, time
from datetime import datetime, timedelta
def processData1( pageFile ):
f = open(pageFile, "r")
page = f.read()
filedate = time.strftime('%m/%d/%Y', time.gmtime(os.path.getmtime(pageFile)))
print filedate
end_date = filedate - datetime.timedelta(days=10)
print end_date
Printing filedateworks, so that date is read correctly from the files. It's the subtraction bit that doesn't seem to be working.
打印filedate工作，以便从文件中正确读取日期。减法位似乎不起作用。
Desired output:
If filedateis 06/11/2013, print end_dateshould yield 06/01/2013.
期望输出：如果filedate是 06/11/2013，print end_date应该 yield 06/01/2013。
采纳答案by Anand S Kumar
When you use time.strftime()you are actually converting a struct_timeto a string.
当您使用时，time.strftime()您实际上是将 a 转换struct_time为字符串。
so filedateis actually a string. When you try to +or -a datetime.timedeltafrom it, you would get an error. Example -
所以filedate实际上是一个字符串。当您尝试使用+或-使用datetime.timedelta它时，您会收到错误消息。例子 -
In [5]: s = time.strftime('%m/%d/%Y', time.gmtime(time.time()))
In [6]: s
Out[6]: '09/01/2015'
In [8]: s - datetime.timedelta(days=10)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-8-fb1d19ed0b02> in <module>()
----> 1 s - datetime.timedelta(days=10)
TypeError: unsupported operand type(s) for -: 'str' and 'datetime.timedelta'
To get a similar behavior to time.gmtime()to can instead use datetime.datetime.utcfromtimestamp(), this would provide a datetime object, from which you can subtract the timedelta.
要获得与 to 类似的行为，time.gmtime()可以改为使用datetime.datetime.utcfromtimestamp()，这将提供一个日期时间对象，您可以从中减去时间增量。
And then if the end result you want is actually a string, you can use datetime.strftime()to convert it to string in required format. Example -
然后，如果您想要的最终结果实际上是一个字符串，则可以使用datetime.strftime()将其转换为所需格式的字符串。例子 -
import os
from datetime import datetime, timedelta
def processData1( pageFile ):
f = open(pageFile, "r")
page = f.read()
filedate = datetime.utcfromtimestamp(os.path.getmtime(pageFile)))
print filedate
end_date = filedate - timedelta(days=10)
print end_date #end_date would be a datetime object.
end_date_string = end_date.strftime('%m/%d/%Y')
print end_date_string
回答by taesu
cleaned up import
清理进口
from datetime import datetime, timedelta
start = '06/11/2013'
start = datetime.strptime(start, "%m/%d/%Y") #string to date
end = start - timedelta(days=10) # date - days
print start,end
