Pandas: convert datetime timestamp to whether it's day or night?

问题

I am trying to determine if its a day or night based on list of timestamps. Will it be correct if I just check the hour between 7:00AM to 6:00PM to classify it as "day", otherwise "night"? Like I have done in below code. I am not sure of this because sometimes its day even after 6pm so whats the accurate way to differentiate between day or night using python?

sample data: (timezone= utc/zulutime)
    timestamps = ['2015-03-25 21:15:00', '2015-06-27 18:24:00', '2015-06-27 18:22:00', '2015-06-27 18:21:00', '2015-07-07 07:53:00']

Code:  
    for timestamp in timestamps:
        time = datetime.datetime.strptime(timestamp, "%Y-%m-%d %H:%M:%S")
        hr, mi = (time.hour, time.minute)
        if hr>=7 and hr<18: print ("daylight")
        else: print ("evening or night")

sample output:
evening or night
evening or night
evening or night
evening or night
daylight

回答1:

You could use pyephem for this task. It's a

Python package for performing high-precision astronomy computations.

You could set the desired location and get the sun altitude. There are multiple definitions for night, depending if it's for civil (-6°), nautical (-12°) or astronomical (-18°) purposes. Just pick a treshold : if the sun is below, it's nighttime!

#encoding: utf8
import ephem
import math
import datetime

sun = ephem.Sun()
observer = ephem.Observer()
# ↓ Define your coordinates here ↓
observer.lat, observer.lon, observer.elevation = '48.730302', '9.149483', 400
# ↓ Set the time (UTC) here ↓
observer.date = datetime.datetime.utcnow()
sun.compute(observer)
current_sun_alt = sun.alt
print(current_sun_alt*180/math.pi)
# -16.8798870431°

回答2:

Unfortunately python's timestamp cannot determine whether it's day or night. This is also because it depends on where you are located and how exactly you define day and night. I'm afraid you will have to get auxiliary data for that.

回答3:

You need to know both latitude and longitude. In fact, if a place is in a deep valley the sunrise there will be later and the sunset earlier. You can pay for this service if you need to obtain it many times per day or simply scrape pages like the one at https://www.timeanddate.com/worldclock/uk/london.

回答4:

As a workaround, there is a free api for adhan times for muslims. It includes sunset and sunrise times exactly. However you still need location coordinates to obtain the data. It is free at the moment.

来源：https://stackoverflow.com/questions/43299500/pandas-convert-datetime-timestamp-to-whether-its-day-or-night

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python

pandas

data-analysis

python-datetime