Question

I understand that repr()‘s purpose is to return a string, that can be used to be evaluated as a python command and return the same object. Unfortunately, pytz does not seem to be very friendly with this function, although it should be quite easy, since pytz instances are created with a single call:

import datetime, pytz
now = datetime.datetime.now(pytz.timezone('Europe/Berlin'))
repr(now)

returns:

datetime.datetime(2010, 10, 1, 13, 2, 17, 659333, tzinfo=<DstTzInfo 'Europe/Berlin' CEST+2:00:00 DST>)

which cannot be simply copied to another ipython windows and evaluated, because it returns a Syntax Error on the tzinfo attribute.

Is there any simple way to let it print:

datetime.datetime(2010, 10, 1, 13, 2, 17, 659333, tzinfo=pytz.timezone('Europe/Berlin'))

when the 'Europe/Berlin' string is already clearly visible in the original output of repr()?

Answer 1

import datetime
import pytz
import pytz.tzinfo

def tzinfo_repr(self):
    return 'pytz.timezone({z})'.format(z=self.zone)
pytz.tzinfo.DstTzInfo.__repr__=tzinfo_repr

berlin=pytz.timezone('Europe/Berlin')
now = datetime.datetime.now(berlin)
print(repr(now))
# datetime.datetime(2010, 10, 1, 14, 39, 4, 456039, tzinfo=pytz.timezone("Europe/Berlin"))

Note that pytz.timezone("Europe/Berlin") in the summer can mean something different than pytz.timezone("Europe/Berlin")) in the winter, due to daylight savings time. So the monkeypatched __repr__ is not a correct representation of self for all time. But it should work (except for extreme corner cases) during the time it takes to copy and paste into IPython.

---

An alternative approach would be to subclass datetime.tzinfo:

class MyTimezone(datetime.tzinfo):
    def __init__(self,zone):
        self.timezone=pytz.timezone(zone)
    def __repr__(self):
        return 'MyTimezone("{z}")'.format(z=self.timezone.zone)
    def utcoffset(self, dt):
        return self.timezone._utcoffset
    def tzname(self, dt):
        return self.timezone._tzname
    def dst(self, dt):
        return self.timezone._dst

berlin=MyTimezone('Europe/Berlin')
now = datetime.datetime.now(berlin)
print(repr(now))
# datetime.datetime(2010, 10, 1, 19, 2, 58, 702758, tzinfo=MyTimezone("Europe/Berlin"))