RFC 1123 Date Representation in Python?

Is there a fairly easy way to convert a datetime object into an RFC 1123 (HTTP/1.1) date/time string, i.e. a string with the format

Sun, 06 Nov 1994 08:49:37 GMT

Using strftime does not work, since the strings are locale-dependant. Do I have to build the string by hand?

You can use wsgiref.handlers.format_date_time from the stdlib which does not rely on locale settings

from wsgiref.handlers import format_date_time
from datetime import datetime
from time import mktime

now = datetime.now()
stamp = mktime(now.timetuple())
print format_date_time(stamp) #--> Wed, 22 Oct 2008 10:52:40 GMT

You can use email.utils.formatdate from the stdlib which does not rely on locale settings

from email.utils import formatdate
from datetime import datetime
from time import mktime

now = datetime.now()
stamp = mktime(now.timetuple())
print formatdate(
    timeval     = stamp,
    localtime   = False,
    usegmt      = True
) #--> Wed, 22 Oct 2008 10:55:46 GMT

If you can set the locale process wide then you can do:

import locale, datetime

locale.setlocale(locale.LC_TIME, 'en_US')
datetime.datetime.utcnow().strftime('%a, %d %b %Y %H:%M:%S GMT')

If you don't want to set the locale process wide you could use Babel date formating

from datetime import datetime
from babel.dates import format_datetime

now = datetime.utcnow()
format = 'EEE, dd LLL yyyy hh:mm:ss'
print format_datetime(now, format, locale='en') + ' GMT'

A manual way to format it which is identical with wsgiref.handlers.format_date_time is:

def httpdate(dt):
    """Return a string representation of a date according to RFC 1123
    (HTTP/1.1).

    The supplied date must be in UTC.

    """
    weekday = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"][dt.weekday()]
    month = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep",
             "Oct", "Nov", "Dec"][dt.month - 1]
    return "%s, %02d %s %04d %02d:%02d:%02d GMT" % (weekday, dt.day, month,
        dt.year, dt.hour, dt.minute, dt.second)

You can use the formatdate() function from the Python standard email module:

from email.utils import formatdate
print formatdate(timeval=None, localtime=False, usegmt=True)

Gives the current time in the desired format:

Wed, 22 Oct 2008 10:32:33 GMT

In fact, this function does it "by hand" without using strftime()

If anybody reading this is working on a Django project, Django provides a function django.utils.http.http_date(epoch_seconds).

from django.utils.http import http_date

some_datetime = some_object.last_update
response['Last-Modified'] = http_date(some_datetime.timestamp())

You can set LC_TIME to force stftime() to use a specific locale:

>>> locale.setlocale(locale.LC_TIME, 'en_US')
'en_US'
>>> datetime.datetime.now().strftime(locale.nl_langinfo(locale.D_T_FMT))
'Wed 22 Oct 2008 06:05:39 AM '

Well, here is a manual function to format it:

def httpdate(dt):
    """Return a string representation of a date according to RFC 1123
    (HTTP/1.1).
    
    The supplied date must be in UTC.

    """
    weekday = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"][dt.weekday()]
    month = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep",
             "Oct", "Nov", "Dec"][dt.month - 1]
    return "%s, %02d %s %04d %02d:%02d:%02d GMT" % (weekday, dt.day, month,
        dt.year, dt.hour, dt.minute, dt.second)