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Edit: Well my previous suggestions don't work with the fact that get_response has to be called with the correct timezone active.

• Is the time_zone attribute from GeoIP2 always compatible with pytz btw.?

Perhaps the following would work, verifying the cookie value only once and discarding it if it doesn't fit:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
if cookie not in pytz.all_timezones_set:
    cookie = None

if not cookie and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

if cookie:
    timezone.activate(pytz.timezone(cookie))

response = self.get_response(request)
if cookie:
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response

So, downside is a lot of mentions of cookie, upside is that it's not more costly what you had before and the timezone is only set once.

Last point, if anything like this happens to be needed more than once, put it into separate functions. This snippet is a bit short to make that call.

Edit: Well my previous suggestions don't work with the fact that get_response has to be called with the correct timezone active.

• Is the time_zone attribute from GeoIP2 always compatible with pytz btw.?

Perhaps the following would work, verifying the cookie value only once and discarding it if it doesn't fit:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
if cookie not in pytz.all_timezones_set:
    cookie = None

if not cookie and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

if cookie:
    timezone.activate(pytz.timezone(cookie))

response = self.get_response(request)
if cookie:
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response

So, downside is a lot of mentions of cookie, upside is that it's not more costly what you had before and the call to set the timezone is only there once.

Last point, if anything like this happens to be needed more than once, put it into separate functions. This snippet is a bit short to make that call.

I'd rearrange a bit first, set_cookie isn't really useful, that block at the end can just be inlined:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
response = self.get_response(request)

if cookie and cookie in pytz.all_timezones_set:
    timezone.activate(pytz.timezone(cookie))
elif request.ip:
    try:
        time_zone = GeoIP2().city(request.ip).time_zone
        if time_zone:
            timezone.activate(pytz.timezone(time_zone))
            response.set_cookie(TIMEZONE_COOKIE_NAME, time_zone)
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

return response

From an efficiency and readability standpoint that's actually fine IMO, I wouldn't necessarily change it more.

However, consider the two logical blocks, "get a timezone in pytz format" and "set the timezone cookie" as separate code blocks too e.g.:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)

if cookie not in pytz.all_timezones_set and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

response = self.get_response(request)
if cookie in pytz.all_timezones_set:
    timezone.activate(pytz.timezone(cookie))
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response

My concern would be here that some work is duplicated to get slightly better readability, instead perhaps the following would be better, verifying the cookie value only once and discarding it if it doesn't fit:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
if cookie no in pytz.all_timezones_set:
    cookie = None

if not cookie and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)
 
response = self.get_response(request)
if cookie:
    timezone.activate(pytz.timezone(cookie))
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response

Edit: Well my previous suggestions don't work with the fact that get_response has to be called with the correct timezone active.

Perhaps the following would work, verifying the cookie value only once and discarding it if it doesn't fit:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
if cookie not in pytz.all_timezones_set:
    cookie = None

if not cookie and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

if cookie:
    timezone.activate(pytz.timezone(cookie)) 

response = self.get_response(request)
if cookie:
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response

So, downside is a lot of mentions of cookie, upside is that it's not more costly what you had before and the timezone is only set once.

I'd rearrange a bit first, set_cookie isn't really useful, that block at the end can just be inlined:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
response = self.get_response(request)

if cookie and cookie in pytz.all_timezones_set:
    timezone.activate(pytz.timezone(cookie))
elif request.ip:
    try:
        time_zone = GeoIP2().city(request.ip).time_zone
        if time_zone:
            timezone.activate(pytz.timezone(time_zone))
            response.set_cookie(TIMEZONE_COOKIE_NAME, time_zone)
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

return response

From an efficiency and readability standpoint that's actually fine IMO, I wouldn't necessarily change it more.

• Is the time_zone attribute from GeoIP2 always compatible with pytz btw.?

However, consider the two logical blocks, "get a timezone in pytz format" and "set the timezone cookie" as separate code blocks too e.g.:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)

if cookie not in pytz.all_timezones_set and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

response = self.get_response(request)
if cookie in pytz.all_timezones_set:
    timezone.activate(pytz.timezone(cookie))
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response

My concern would be here that some work is duplicated to get slightly better readability, instead perhaps the following would be better, verifying the cookie value only once and discarding it if it doesn't fit:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
if cookie no in pytz.all_timezones_set:
    cookie = None

if not cookie and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

response = self.get_response(request)
if cookie:
    timezone.activate(pytz.timezone(cookie))
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response

I'd rearrange a bit first, set_cookie isn't really useful, that block at the end can just be inlined:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
response = self.get_response(request)

if cookie and cookie in pytz.all_timezones_set:
    timezone.activate(pytz.timezone(cookie))
elif request.ip:
    try:
        time_zone = GeoIP2().city(request.ip).time_zone
        if time_zone:
            timezone.activate(pytz.timezone(time_zone))
            response.set_cookie(TIMEZONE_COOKIE_NAME, time_zone)
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

return response

From an efficiency and readability standpoint that's actually fine IMO, I wouldn't necessarily change it more.

• Is the time_zone attribute from GeoIP2 always compatible with pytz btw.?

However, consider the two logical blocks, "get a timezone in pytz format" and "set the timezone cookie" as separate code blocks too e.g.:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)

if cookie not in pytz.all_timezones_set and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

response = self.get_response(request)
if cookie in pytz.all_timezones_set:
    timezone.activate(pytz.timezone(cookie))
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response

My concern would be here that some work is duplicated to get slightly better readability, instead perhaps the following would be better, verifying the cookie value only once and discarding it if it doesn't fit:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
if cookie no in pytz.all_timezones_set:
    cookie = None

if not cookie and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

response = self.get_response(request)
if cookie:
    timezone.activate(pytz.timezone(cookie))
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response

Last point, if anything like this happens to be needed more than once, put it into separate functions. This snippet is a bit short to make that call.