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Date: Sat, 24 Dec 2011 06:04:19 +0000
Subject: Re: modifying a time.struct_time
From: Jason Friedman <jason@powerpull.net>
To: Chris Angelico <rosuav@gmail.com>
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On Fri, Dec 16, 2011 at 10:44 AM, Chris Angelico <rosuav@gmail.com> wrote:
> On Fri, Dec 16, 2011 at 8:45 PM, Ulrich Eckhardt
> <ulrich.eckhardt@dominolaser.com> wrote:
>> I'm trying to create a struct_time that is e.g. one year ahead or a mont=
h
>> back in order to test some parsing/formatting code with different dates.
>
> Do you need it to be one exact calendar year, or would it make sense
> to add/subtract integers from a Unix time?
>
> t =3D time.time() + 365*86400 =A0 # Not actually a year ahead, it's 365 d=
ays ahead
> t =3D time.localtime(t) =A0# if you want a struct_time
>
> ChrisA
> --

Not particularly elegant, but I believe accurate and relying only on
the stated struct_time contract:

#!/usr/bin/env python
# 2.7.2
import time, itertools
def is_local_time_different_by_one_year(time1, time2):
    if abs(time1.tm_year - time2.tm_year) !=3D 1:
        return False
    if abs(time1.tm_mon  - time2.tm_mon ) !=3D 0:
        return False
    if abs(time1.tm_mday - time2.tm_mday) !=3D 0:
        return False
    if abs(time1.tm_hour - time2.tm_hour) !=3D 0:
        return False
    if abs(time1.tm_min  - time2.tm_min ) !=3D 0:
        return False
    if abs(time1.tm_sec  - time2.tm_sec ) !=3D 0:
        return False
    return True

t =3D time.time()
time1 =3D time.localtime(t)
print("Local time is {}.".format(time1))
for i in itertools.count(0):
    t +=3D 1 # Add one second until we have reached next year
    time2 =3D time.localtime(t)
    if is_local_time_different_by_one_year(time1, time2):
        print("One year later is {}".format(time2))
        break


Not exactly a speed demon, either:
$ time python timediff.py
Local time is time.struct_time(tm_year=3D2011, tm_mon=3D12, tm_mday=3D24,
tm_hour=3D5, tm_min=3D57, tm_sec=3D44, tm_wday=3D5, tm_yday=3D358, tm_isdst=
=3D0).
One year later is time.struct_time(tm_year=3D2012, tm_mon=3D12,
tm_mday=3D24, tm_hour=3D5, tm_min=3D57, tm_sec=3D44, tm_wday=3D0, tm_yday=
=3D359,
tm_isdst=3D0)

real	3m8.922s
user	2m2.470s
sys	1m1.760s