How to print timedelta consistently (i.e. formatted)

Question

I have this code that prints the time difference in milliseconds.

#!/usr/bin/python
import datetime
import sys

date1= datetime.datetime.strptime('20231107-08:52:53.539', '%Y%m%d-%H:%M:%S.%f')
date2= datetime.datetime.strptime('20231107-08:52:53.537', '%Y%m%d-%H:%M:%S.%f')
diff = date1-date2
sys.stdout.write(str(diff) + '\t')
date1= datetime.datetime.strptime('20231107-08:52:53.537', '%Y%m%d-%H:%M:%S.%f')
date2= datetime.datetime.strptime('20231107-08:52:53.537', '%Y%m%d-%H:%M:%S.%f')
diff = date1-date2
sys.stdout.write(str(diff) + '\t')
date1= datetime.datetime.strptime('20231107-08:52:53.532', '%Y%m%d-%H:%M:%S.%f')
date2= datetime.datetime.strptime('20231107-08:52:53.537', '%Y%m%d-%H:%M:%S.%f')
diff = date1-date2
sys.stdout.write(str(diff) + '\n')

And it prints this, without consistency

$ python ./prntdatetest.py

0:00:00.002000 <tab> 0:00:00 <tab> -1 day, 23:59:59.995000

I want this to be printed like this

00:00:00.002 <tab> 00:00:00.000 <tab> -0:00:00.005

I do not want to use the print but i want to use stdout.write

How can I do this?

Answer 1

You can define the following formatting function:

def format_diff(diff):
    sign = '-' if diff < datetime.timedelta(0) else ''
    seconds = abs(diff.total_seconds())
    return f'{sign}{seconds//60//60:02.0f}:{seconds//60%60:02.0f}:{seconds%60:06.03f}'

#!/usr/bin/python
import datetime
import sys

date1= datetime.datetime.strptime('20231107-08:52:53.539', '%Y%m%d-%H:%M:%S.%f')
date2= datetime.datetime.strptime('20231107-08:52:53.537', '%Y%m%d-%H:%M:%S.%f')
diff = date1-date2
sys.stdout.write(format_diff(diff) + '\t')
date1= datetime.datetime.strptime('20231107-08:52:53.537', '%Y%m%d-%H:%M:%S.%f')
date2= datetime.datetime.strptime('20231107-08:52:53.537', '%Y%m%d-%H:%M:%S.%f')
diff = date1-date2
sys.stdout.write(format_diff(diff) + '\t')
date1= datetime.datetime.strptime('20231107-08:52:53.532', '%Y%m%d-%H:%M:%S.%f')
date2= datetime.datetime.strptime('20231107-08:52:53.537', '%Y%m%d-%H:%M:%S.%f')
diff = date1-date2
sys.stdout.write(format_diff(diff) + '\n')

Output:

00:00:00.002    00:00:00.000    -00:00:00.005

Note: that handles values up to on day. For >= 1 day deltas, you need to update the function.

Answer 2

use diff.total_seconds() to get the absolute number of seconds in a timedelta object.

From there, use modulo and division to separate hours, minutes and seconds:

date1= datetime.datetime.strptime('20231107-08:52:53.532', '%Y%m%d-%H:%M:%S.%f')
date2= datetime.datetime.strptime('20231107-08:52:53.537', '%Y%m%d-%H:%M:%S.%f')
diff = date1-date2

secs = diff.total_seconds()
signal = "-" if secs < 0 else ""
secs = abs(secs)
sys.stdout.write(f"{signal}{secs//86400:.0f}:{secs % 86400 // 3600:02.0f}:{secs % 3600 // 60:02.0f}:{secs % 60:02.03f}\n")

Of course you will be better if you factor out the above string formatting to a separate helper function.