1 00:00:05,420 --> 00:00:09,100 so in this video we're going to use the Python Library the module that we've 2 00:00:09,100 --> 00:00:15,880 installed in the previous video so if you haven't installed pytz module you 3 00:00:15,880 --> 00:00:19,050 need to go away and do that before this will work because otherwise you get some 4 00:00:19,050 --> 00:00:22,510 weird errors and you won't be able to use the module so how do we check that 5 00:00:22,510 --> 00:00:25,070 that model has been installed successfully 6 00:00:25,070 --> 00:00:29,690 well lets write up a test program to make sure it's all 7 00:00:29,690 --> 00:00:35,100 working so type....we should be able to type pytz and use it as we 8 00:00:35,100 --> 00:00:41,030 normally used an import.... so you should find 9 00:00:41,030 --> 00:00:48,510 that will work now that we have installed that and lets display the current time in moscow I am going to import date time 10 00:00:48,510 --> 00:00:50,540 as well 11 00:00:50,540 --> 00:01:03,470 and will put... 12 00:01:03,470 --> 00:01:15,130 ....so we are going to display the time zone for 13 00:01:15,130 --> 00:01:24,710 moscow and we will put... 14 00:01:24,710 --> 00:01:39,590 ..... 15 00:01:39,590 --> 00:01:42,990 .....and that's not actually an error that you can see there that's just it 16 00:01:42,990 --> 00:01:48,170 showing in a different color and we will now put.... 17 00:01:48,170 --> 00:02:04,740 .... 18 00:02:04,740 --> 00:02:12,400 ..... 19 00:02:12,400 --> 00:02:20,490 ...... 20 00:02:20,490 --> 00:02:28,620 ...so there is our program so lets right click it and 21 00:02:28,620 --> 00:02:33,500 incidentally I've created a new Python file called tztest.py I'm still 22 00:02:33,500 --> 00:02:39,670 using the same project we've used for date and time so right click that 23 00:02:39,670 --> 00:02:44,400 and run it so we make sure we're running this file and the time in europe moscow 24 00:02:44,400 --> 00:02:52,780 is january 29th 2016 and its 5 am there and if you can 25 00:02:52,780 --> 00:02:57,410 just confirm that we can go to Google and and search for current time 26 00:02:57,410 --> 00:03:08,190 moscow 5:28 a.m. GMT +3 29th of January so you can see that 27 00:03:08,190 --> 00:03:11,610 we've got that working quite nicely so close that down now 28 00:03:11,610 --> 00:03:17,130 obviously from pytz module we used the timezone method on line 6 and that's because 29 00:03:17,130 --> 00:03:22,610 the pytz only deals with time zone information by using pytz to create 30 00:03:22,610 --> 00:03:28,040 a tzinfo object then we then used on line 7 to calculate the 31 00:03:28,040 --> 00:03:31,460 local time in any country so you could change this to any country and do the same 32 00:03:31,460 --> 00:03:36,140 now from pytz we can use the timezone method to get the tzinfo object for any 33 00:03:36,140 --> 00:03:40,140 chosen country but the required string is difficult to sort if you wanted to 34 00:03:40,140 --> 00:03:43,760 provide the entire list to a user so is moscow really in Europe and will most 35 00:03:43,760 --> 00:03:47,130 people really know to look there what we can do is we can print the 36 00:03:47,130 --> 00:03:52,020 entire list of valid strings that the pytz.timezone method accepts 37 00:03:52,020 --> 00:03:57,850 quite easily and the reason we can do that is it quite helpfully provides a Python list 38 00:03:57,850 --> 00:04:04,440 called all_timezones so we could put something.... 39 00:04:04,440 --> 00:04:15,910 ...so run that now you can see we got a list of everything for the various 40 00:04:15,910 --> 00:04:20,790 countries a heap of Australia as you can see but quite a few different ones are showing there 41 00:04:20,790 --> 00:04:25,630 the other thing I actually do also is provide a dictionary of country names 42 00:04:25,630 --> 00:04:30,580 who's keys the iso316 country code in other words GB for britain AU for 43 00:04:30,580 --> 00:04:36,740 Australia etc so we can put... 44 00:04:36,740 --> 00:04:53,370 .... 45 00:04:53,370 --> 00:04:58,750 ....so if we run and have a look at the results you can see we got the identifier to 46 00:04:58,750 --> 00:05:10,450 the left and then the actual name to the right AU for Australia US for United States GB for 47 00:05:10,450 --> 00:05:14,790 Great Britain etcetera now the thing to remember here is that the list of 48 00:05:14,790 --> 00:05:19,930 countries isn't actually good enough for getting the timezone and that's because many countries 49 00:05:19,930 --> 00:05:23,960 have got more than one timezone and so it is possible to retrieve a list of all 50 00:05:23,960 --> 00:05:27,930 the time zones for a country code and display them after the country name so 51 00:05:27,930 --> 00:05:33,170 we might be tempted to just use the same key then pytz.time_zone dictionary 52 00:05:33,170 --> 00:05:40,540 something like this you could do... 53 00:05:40,540 --> 00:05:55,180 ...... 54 00:05:55,180 --> 00:06:07,270 ..... 55 00:06:07,270 --> 00:06:13,430 ....so you could try that so its probably reasonably to expect both dictionaries to 56 00:06:13,430 --> 00:06:19,580 contain the same keys so run that we've actually got an error here so the 57 00:06:19,580 --> 00:06:24,020 program actually ran until it hit the Key BV at which point it crashed 58 00:06:24,020 --> 00:06:28,570 and that's because there is no time zone defined for Ireland so as its 59 00:06:28,570 --> 00:06:32,260 inhabited it's a bit strange that you have keys in the country names in the list at all but we 60 00:06:32,260 --> 00:06:34,620 can't really blame pytz for that 61 00:06:34,620 --> 00:06:39,760 sorry we can't really use the same keys as you can see there now the timezone data 62 00:06:39,760 --> 00:06:44,340 itself it comes from a data base that's maintained by 63 00:06:44,340 --> 00:06:48,800 IANA in which is the internet assigned names authority and I'm just gonna 64 00:06:48,800 --> 00:06:57,770 bring up that link in a browser and it's these guys and that's where the time zone 65 00:06:57,770 --> 00:07:02,050 date is coming from now it's often referred to as the Olsen database and 66 00:07:02,050 --> 00:07:06,860 that's named after its creator Arthur David Olsen the database contains a history of 67 00:07:06,860 --> 00:07:10,930 timezone and Daylight Saving Time changes and is pretty much considered the 68 00:07:10,930 --> 00:07:15,150 definitive source of information on these now it is kept up-to-date and used to 69 00:07:15,150 --> 00:07:19,400 update the time zone information on most computers although that said Windows 70 00:07:19,400 --> 00:07:23,510 does things slightly differently now as long as your computer is receiving those updates 71 00:07:23,510 --> 00:07:27,920 the local timezone database should be kept up to date but if you got a time for 72 00:07:27,920 --> 00:07:35,040 moscow that was four hours behind UTC rather than 3 as you see in our pytz example 73 00:07:35,040 --> 00:07:39,020 that means your probably running Windows XP which is no longer updated and therefore missing 74 00:07:39,020 --> 00:07:43,040 last year's change because its out of date so with that said how to we get 75 00:07:43,040 --> 00:07:47,580 around this well we can do is go back to the code is we can write our code a bit more 76 00:07:47,580 --> 00:07:52,300 defensively by using the Get Command or the get method I should say and if you 77 00:07:52,300 --> 00:07:55,340 remember from the lectures on dictionaries this returns none 78 00:07:55,340 --> 00:07:59,540 rather than an exception if the keys is not in the dictionary so we could take a 79 00:07:59,540 --> 00:08:03,340 copy of this again well I'll just make a change because obviously it's crashing 80 00:08:03,340 --> 00:08:09,950 the problem is is pytz.country_timezones if we change that and instead 81 00:08:09,950 --> 00:08:17,020 of putting and make the a .get with x as the parameter that's going to return 82 00:08:17,020 --> 00:08:22,200 none in the case of there being a time zone nonexistent for a particular 83 00:08:22,200 --> 00:08:28,040 country so you can run that and see what happens now we don't get a crash and you 84 00:08:28,040 --> 00:08:33,520 can see we got time zones now so we come back up Australia and you notice we got multiple time 85 00:08:33,520 --> 00:08:37,480 zones are quite happily working now Australian Lord Howe Macquarie Hobart 86 00:08:37,480 --> 00:08:42,760 etc as we go across there is quite a few there and likewise for some of the other ones 87 00:08:42,760 --> 00:08:47,100 as well Australia America Antarctica etc so its obviously now working 88 00:08:47,100 --> 00:08:48,320 if you go back to B 89 00:08:48,320 --> 00:08:57,000 Bouvet Island is still showing on the list but now is not getting any timezone information and that's 90 00:08:57,000 --> 00:09:01,730 because we got none returned and prevented the program from crashing now if you 91 00:09:01,730 --> 00:09:05,160 needed to perform a more complicated operation than just printing the list 92 00:09:05,160 --> 00:09:10,160 what we could do was split up the access to country_timezones and then check if 93 00:09:10,160 --> 00:09:14,220 that the key is in the dictionary first so 94 00:09:14,220 --> 00:09:25,840 actual what I might do is just comments one of this out now take a copy of that but then 95 00:09:25,840 --> 00:09:32,760 ccomment that out and you can come back and refer to it if you need to so lets go back and paste that command 96 00:09:32,760 --> 00:09:37,980 again what we want to do is to start is removing the time zones from this 97 00:09:37,980 --> 00:09:38,780 part of the 98 00:09:38,780 --> 00:09:45,910 screen here now so I'm going to...so we just got 2 we are gong to print x 99 00:09:45,910 --> 00:09:54,320 as the parameters and the format pytz.country_timezone.get(x) we are going to leave that all together 100 00:09:54,320 --> 00:10:05,570 we gonna put..... 101 00:10:05,570 --> 00:10:11,680 .....if you 102 00:10:11,680 --> 00:10:18,750 get an entry in time zone if that is the case we are going to print... 103 00:10:18,750 --> 00:10:28,450 ...so this time we are actually gonna 104 00:10:28,450 --> 00:10:33,710 show that instead of just using the default which was just to print 105 00:10:33,710 --> 00:10:41,590 anything so we can do that and run this...and you 106 00:10:41,590 --> 00:10:46,770 see we quite happily get the same information we come up here we now got Bouvet Island 107 00:10:46,770 --> 00:10:53,940 no time zone defined and you can see its working nicely and it is a more defensive 108 00:10:53,940 --> 00:10:58,150 way of doing it and more complicated but you can see that by splitting the access 109 00:10:58,150 --> 00:11:00,770 to country_timezone and then checking 110 00:11:00,770 --> 00:11:05,790 the keys in the dictionary first were able to process it that way now one thing 111 00:11:05,790 --> 00:11:09,790 we might want to do is to print the time for each of the timezones in each country 112 00:11:09,790 --> 00:11:15,190 that's fairly easy to do now that we've got pytz to use with date time so what we gonna 113 00:11:15,190 --> 00:11:20,950 do is print each time on a new line indented by 2 tab stops and so 114 00:11:20,950 --> 00:11:24,920 that we can remove the and parameter in the print statement on line 12 so we gonna 115 00:11:24,920 --> 00:11:29,730 do is come up to here after the if instead of just doing a print what 116 00:11:29,730 --> 00:11:39,650 we're going to do is put.... 117 00:11:39,650 --> 00:11:53,280 ...... 118 00:11:53,280 --> 00:12:03,970 ........ 119 00:12:03,970 --> 00:12:08,430 .......and I'm going to print something a bit different 120 00:12:08,430 --> 00:12:15,140 than before and will put some tabs in so..... 121 00:12:15,140 --> 00:12:38,060 ..... 122 00:12:38,060 --> 00:12:42,510 ...so no we've done that we should be able to run this and see 123 00:12:42,510 --> 00:12:47,070 the result and you can see we've now actually got to the actual current time 124 00:12:47,070 --> 00:12:50,960 for that time zone showing on the screen that is pretty cool as you can see if we come 125 00:12:50,960 --> 00:12:57,010 back and check Australia we got Adelaide current times 13:11 if I just open this 126 00:12:57,010 --> 00:13:03,520 up friday 1:11 p.m. 13:11 so that is working nicely ok so I'm gonna end this video 127 00:13:03,520 --> 00:13:06,120 here now because it's getting a little bit long in the next few video we're going to 128 00:13:06,120 --> 00:13:11,290 continue on our discussions and understanding about using pytz 129 00:13:11,290 --> 00:13:16,330 and introduce you to the localize function and to some other conversion 130 00:13:16,330 --> 00:13:20,060 that should be quite interesting for you so we'll see you in the next video