午夜的Python时间比较 [英] Python time comparison at midnight

问题描述

我必须将时间保存为 AM PM 格式.

I have to save the time in AM PM format.

但是我在决定如何输入午夜时间时遇到了麻烦.

But i am having trouble in deciding how to enter midnight time.

假设时间是第二天早上9点至凌晨6点.我必须将它分为日常基础.像这样

Suppose the time is 9PM to 6AM next morning. I have to divide it into day to day basis . Like this

t1 = datetime.datetime.strptime('09:00PM', '%I:%M%p').time()

t2 = datetime.datetime.strptime('12:00AM', '%I:%M%p').time()

t3 = datetime.datetime.strptime('06:00AM', '%I:%M%p').time()

现在我想知道t2是否应该

Now i want to know whether the t2 should be

12:00 AM 或 11.59PM

如果我是12:00 AM，那么如果 9pm>我无法比较.上午12点，但11.59看起来很奇怪，或者可能是正确的方式

If i do 12:00AM then i can't compare if 9pm > 12am but 11.59 looks odd or may be it is right way

推荐答案

您应始终使用 00:00 (或 12:00 AM )表示午夜.

You should always use 00:00 (or 12:00 AM) to represent midnight.

使用 23:59 (或 11:59 PM )存在问题，原因有几个:

Using 23:59 (or 11:59 PM) is problematic for a couple of reasons:

• 精度在比较中很重要. 23:59:01 是不是在午夜之前?怎么样 23:59:59.9999 ?

• Precision matters in the comparison. Is 23:59:01 not before midnight? What about 23:59:59.9999?

您选择的任何精度都会拖延工期计算.考虑到午夜的 10:00 pm 是2小时，而不是1小时59分钟.

Duration calculation will be thrown off by whatever precision you chose. Consider that 10:00 pm to midnight is 2 hours, not 1 hour and 59 minutes.

为避免这些问题，您应始终将时间间隔视为半开间隔.即，范围具有包含的开始和包含的结束.在间隔符号中: [开始，结束)

To avoid these problems, you should always treat time intervals as half-open intervals. That is, the range has an inclusive start, and an exclusive end. In interval notation: [start, end)

现在要穿越午夜边界:

• 在比较与日期关联的时间时，您可以直接比较:

• When you are comparing times that are associated with a date, you can just compare directly:

[2015-01-01T21:00,  2015-01-02T06:00) = 9 hours
 2015-01-01T21:00 < 2015-01-02T06:00 

没有日期时，可以确定持续时间，但不能确定顺序！

When you do not have a date, you can determine duration, but you cannot determine order!

[21:00, 06:00) = 9 hours
 21:00 < 06:00  OR  21:00 > 06:00

您能做的最好的事情就是确定时间是否在该范围所覆盖的点之间 .

The best you can do is determine whether a time is between the points covered by the range.

Both 23:00 and 01:00 are in the range [21:00, 06:00)
21:00 is also in that range, but 06:00 is NOT.

考虑一个时钟.它被建模为圆形，而不是直线.

Think about a clock. It's modeled as a circle, not as a straight line.

要计算可以跨越午夜的仅时间间隔的持续时间，请使用以下伪代码:

To calculate duration of a time-only interval that can cross midnight, use the following pseudocode:

if (start <= end)
    duration = end - start
else
    duration = end - start + 24_hours

或更简单地说:

duration = (end - start + 24_hours) % 24_hours

要确定仅时间值是否落在可以跨越午夜的仅时间间隔内，请使用以下伪代码:

To determine whether a time-only value falls within a time-only interval that can cross midnight, use this pseudocode:

if (start <= end)
    is_between = start <= value AND end > value
else
    is_between = start <= value OR  end > value

请注意，在上面的伪代码中，我指的是数值的幅值(以数字方式进行比较)，而不是逻辑时间值，如前所述，如果没有参考日期，则逻辑时间值不能独立进行比较

Note that in the above pseudocode, I am referring to the magnitude of the values, as compared numerically - not the logical time values which, as said earlier, cannot be compared independently without a reference date.

此外，我的日期和时间基础课程涵盖了很多内容(最后，在使用范围"中).

Also, much of this is covered in my Date and Time Fundamentals course on Pluralsight (towards the very end, in "Working With Ranges").

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