如何在python中的datetime.timedelta上执行divison？

Question

我希望能够做到以下几点:

num_intervals = (cur_date - previous_date) / interval_length

要么

print (datetime.now() - (datetime.now() - timedelta(days=5))) 
      / timedelta(hours=12)
# won't run, would like it to print '10'

但是timedeltas不支持除法运算.有没有办法可以为timedeltas实现divison？

编辑:看起来这是添加到Python 3.2(感谢rincewind!):http://bugs.python.org/issue2706

Answer 1

整数除法和乘法似乎开箱即用:

>>> from datetime import timedelta
>>> timedelta(hours=6)
datetime.timedelta(0, 21600)
>>> timedelta(hours=6) / 2
datetime.timedelta(0, 10800)

Answer 2

当然,只需转换为几秒钟(分钟,毫秒,小时,选择单位)并进行划分.

编辑(再次):所以你不能分配给timedelta.__div__.试试这个,然后:

divtdi = datetime.timedelta.__div__
def divtd(td1, td2):
    if isinstance(td2, (int, long)):
        return divtdi(td1, td2)
    us1 = td1.microseconds + 1000000 * (td1.seconds + 86400 * td1.days)
    us2 = td2.microseconds + 1000000 * (td2.seconds + 86400 * td2.days)
    return us1 / us2 # this does integer division, use float(us1) / us2 for fp division

并将此纳入纳迪亚的建议:

class MyTimeDelta:
    __div__ = divtd

用法示例:

>>> divtd(datetime.timedelta(hours = 12), datetime.timedelta(hours = 2))
6
>>> divtd(datetime.timedelta(hours = 12), 2)
datetime.timedelta(0, 21600)
>>> MyTimeDelta(hours = 12) / MyTimeDelta(hours = 2)
6

当然,你甚至可以命名(或别名)你的自定义类,timedelta以便它被用来代替真实的timedelta,至少在你的代码中.