字符串转换为日期时间时区

Question

我想对两个时间字符串之间的一些点进行线性插值。

所以我尝试将字符串转换为日期时间，然后插入一些点，然后将日期时间转换为字符串。但似乎时区不正确。

在下面的例子中。我想在 9-28 11:07:57.435" 和 "9-28 12:00:00.773".

之间插入一个点

#!/usr/bin/env python
import numpy as np
from time import mktime
from datetime import datetime

#-----------------------------------------#
def main():
    dtstr = [
"9-28 11:07:57.435",
"9-28 12:00:00.773"
]
    print "input",dtstr
    dtlst = str2dt(dtstr)
    floatlst = dt2float(dtlst)

    bins = 3
    x1 = list(np.arange(floatlst[0],floatlst[-1],(floatlst[-1]-floatlst[0])/bins))
    dtlst = float2dt(x1)
    dtstr = dt2str(dtlst)
    print "output",dtstr
    return

def str2dt(strlst):
    dtlst = [datetime.strptime("2014-"+i, "%Y-%m-%d %H:%M:%S.%f") for i in strlst]
    return dtlst

def dt2float(dtlst):
    floatlst = [mktime(dt.timetuple()) for dt in dtlst]
    return floatlst

def dt2str(dtlst):
    dtstr = [dt.strftime("%Y-%m-%d %H:%M:%S %Z%z") for dt in dtlst]
    return dtstr

def float2dt(floatlst):
    dtlst = [datetime.utcfromtimestamp(seconds) for seconds in floatlst]
    return dtlst

#-----------------------------------------#
if __name__ == "__main__":
    main()

输出如下：

input ['9-28 11:07:57.435', '9-28 12:00:00.773']
output ['2014-09-28 16:07:57 ', '2014-09-28 16:25:18 ', '2014-09-28 16:42:39 ']

这里有两个问题：

输入和输出有 4 小时的差异（9-28 16:07:57 到 9-28 11:07:57）。我猜它是由时区引起的，但不确定如何解决它。
我希望第一个和最后一个点与输入相同，但现在看起来最后一个点小于输入最后一个点(16:42:39 vs 12:00:00)。

Answer 1

Q1。您对时区的看法是正确的，您正在使用 time.mktime 而 converts struct_time to seconds assuming the input is local time, but then using datetime.utcfromtimestamp which (naturally) converts to utc. Use datetime.fromtimestamp 来保持当地时间的所有内容。

Q2。与原生 Python range/xrange 一样，当您执行 numpy.arange(x, y, z) 时，结果以 x 开头并上升到，但不包括 y (except in weird floating point roundoff cases. Don't rely on this behaviour). if you want consistent behaviour on the end points w/ floating values, use numpy.linspace

另一方面，为什么将日期时间转换为秒，然后再返回？ datetime 对象支持加法和减法。以下是我的建议。

from time import mktime, localtime
from datetime import datetime
from copy import copy

def main():
    input_timestrings = ["9-28 11:07:57.435", "9-28 12:00:00.773"]
    input_datetimes = timestrings_to_datestimes(input_timestrings)

    start_datetime = input_datetimes[0]
    end_datetime = input_datetimes[1]

    # subtraction between datetime objects returns a timedelta object
    period_length = end_datetime - start_datetime

    bins = 3

    # operation w/ timedelta objects and datetime objects work pretty much as you'd expect it to
    delta = period_length / bins
    datetimes = list(custom_range(start_datetime, end_datetime + delta, delta))
    output_timestrings = datetimes_to_timestrings(datetimes)

    print output_timestrings
    return

def timestrings_to_datetimes(timestrings):
    datetimes = [datetime.strptime("2014-"+timestring, "%Y-%m-%d %H:%M:%S.%f") for timestring in timestrings]
    return datetimes

def datetimes_to_timestrings(datetimes):
    timestrings = [datetime_.strftime("%Y-%m-%d %H:%M:%S %Z%z") for datetime_ in datetimes]
    return timestrings

def custom_range(start, end, jump):
    x = start
    while x < end:
        yield x
        x = x + jump


if __name__ == "__main__":
    main()

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