Python: from list of decimal to hours / minutes-CodePudding

I have a list like the following:

T = [10.749957462142994, 10.90579301143351, 10.981580990083001]

That contains timestamp in a decimal format

hours =  [ int(x) for x in T ]
minutes =[ (x*60) % 60 for x in T]

print("%d:d"%(hours[0], minutes[0]), "%d:d"%(hours[1], minutes[1]), "%d:d"%(hours[2], minutes[2]))
['10:44', '10:54', '10:58']

I would like to create a list of datetime without years-month-day but just hours and minutes.

I tried this

from datetime import datetime
DT = []
for i,t in enumerate(T):
    string = str("%d:d"%(hours[i], minutes[i]))
    datetime_object = datetime. strptime(string, '%H:%M')
    DT.append(datetime_object)

However DT looks like the following

DT
[datetime.datetime(1900, 1, 1, 10, 44),
 datetime.datetime(1900, 1, 1, 10, 54),
 datetime.datetime(1900, 1, 1, 10, 58)]

How can I remove the information of year, day and month and have something like:

DT
[datetime.datetime( 10, 44),
 datetime.datetime( 10, 54),
 datetime.datetime( 10, 58)]

CodePudding user response：

I've taken a slightly different approach:

from datetime import time, datetime, timedelta
T = [10.749957462142994, 10.90579301143351, 10.981580990083001]
values = [(datetime.min   timedelta(hours=t)).time() for t in T]

timedelta objects support arbitrary floats for the hours. The result is a rather simple 1 line of code.

CodePudding user response：

You can use datetime.time or if you really want to use datetime.datetime then you can get the time only with datatime.datetime.time() method.

CodePudding user response：

Here's a simple way to do it:

import datetime

DUMMY_DATETIME = datetime.datetime(2000, 1, 1, 0, 0)
HOUR = datetime.timedelta(hours=1)

T = [10.749957462142994, 10.90579301143351, 10.981580990083001]
DT = [(DUMMY_DATETIME   hours * HOUR).time() for hours in T]

A timedelta can be multiplied by a float (automatically rounding to microseconds), which lets you easily convert a fractional hours value into a timedelta, without having to manually do the multiplication/division/modulo by 60.

The date part (Y2K) of the DUMMY_DATETIME object is just there to make the operator work (because time timedelta is a TypeError, but datetime timedelta is fine). All that matters is the hours/minutes/seconds part being 0.

The expression DUMMY_DATETIME hours * HOUR thus gives a timestamp that's the specified number of hours after the epoch. And calling .time() on that object gives you the time, without the useless year/month/day part.

>>> DT
[datetime.time(10, 44, 59, 846864), datetime.time(10, 54, 20, 854841), datetime.time(10, 58, 53, 691564)]
>>> [t.strftime('%H:%M') for t in DT]
['10:44', '10:54', '10:58']