WEBVTT 1 00:00:00.440 --> 00:00:01.800 Hi guys and welcome back. 2 00:00:01.800 --> 00:00:03.380 In this video, I wanted to tell you about 3 00:00:03.380 --> 00:00:06.080 the datetime module, which is a built-in module, 4 00:00:06.080 --> 00:00:08.190 part of the Python standard library 5 00:00:08.190 --> 00:00:10.550 that we can use to deal with dates and times 6 00:00:10.550 --> 00:00:12.063 in our Python code. 7 00:00:13.010 --> 00:00:14.883 What is a datetime object? 8 00:00:14.883 --> 00:00:18.240 This is really the main part of the datetime module. 9 00:00:18.240 --> 00:00:20.560 It allows us to store information 10 00:00:20.560 --> 00:00:22.140 about a certain point in time. 11 00:00:22.140 --> 00:00:23.820 Here in the code block on the left 12 00:00:23.820 --> 00:00:25.570 I've imported the daytime module, 13 00:00:25.570 --> 00:00:27.830 and then created a datetime object 14 00:00:27.830 --> 00:00:29.620 which lives inside the datetime module. 15 00:00:29.620 --> 00:00:32.290 So you're gonna see this datetime.datetime stuff 16 00:00:32.290 --> 00:00:34.630 quite often when your working with Python code, 17 00:00:34.630 --> 00:00:36.820 and then inside it you can pass in 18 00:00:36.820 --> 00:00:38.960 your date and time information 19 00:00:38.960 --> 00:00:41.240 with those keyword arguments. 20 00:00:41.240 --> 00:00:43.240 When you print it out, by default, 21 00:00:43.240 --> 00:00:46.980 it prints out the date and time in the ISO format, 22 00:00:46.980 --> 00:00:49.450 but we can look at how you can change that 23 00:00:49.450 --> 00:00:50.830 in just a moment. 24 00:00:50.830 --> 00:00:53.330 You can also compare dates and times 25 00:00:53.330 --> 00:00:56.340 to see which one is greater than another one for example. 26 00:00:56.340 --> 00:00:59.560 With just the usual mathematical operators. 27 00:00:59.560 --> 00:01:02.000 So you can use greater than, less than, and so on. 28 00:01:02.000 --> 00:01:04.860 And we're gonna leave a resource in the resources section 29 00:01:04.860 --> 00:01:06.530 of this lecture with some more information 30 00:01:06.530 --> 00:01:09.850 of what you can do with these datetime objects. 31 00:01:09.850 --> 00:01:12.120 One of the most common things we do with datetime objects 32 00:01:12.120 --> 00:01:15.640 is get the time right now, and this is how you do it. 33 00:01:15.640 --> 00:01:18.160 You use datetime.datetime.now, 34 00:01:18.160 --> 00:01:20.780 and that is gonna give you the current date and time 35 00:01:20.780 --> 00:01:23.740 up to the microsecond, so it's pretty accurate. 36 00:01:23.740 --> 00:01:26.310 This uses your system's local time 37 00:01:26.310 --> 00:01:27.240 to give you the current time, 38 00:01:27.240 --> 00:01:29.983 so it is gonna show you the time that your computer has. 39 00:01:31.690 --> 00:01:34.318 You can also do datetime.datetime.today 40 00:01:34.318 --> 00:01:36.310 to do essentially the same thing, 41 00:01:36.310 --> 00:01:38.570 but it's generally a less precise alternative 42 00:01:38.570 --> 00:01:41.890 because it doesn't have the same support for timezones, 43 00:01:41.890 --> 00:01:43.490 and we're gonna get into what that is 44 00:01:43.490 --> 00:01:44.740 in a couple of videos time, 45 00:01:44.740 --> 00:01:49.150 but I generally recommend using datetime.datetime.now. 46 00:01:49.150 --> 00:01:51.120 Let's take a look at how to display dates 47 00:01:51.120 --> 00:01:54.570 in a different format other than ISO, and how to parse dates 48 00:01:54.570 --> 00:01:57.060 or how to get a string representing a date 49 00:01:57.060 --> 00:01:59.550 and build a datetime object out of them. 50 00:01:59.550 --> 00:02:01.580 Here's how you can display dates. 51 00:02:01.580 --> 00:02:03.650 What we do is we create a date, for example, 52 00:02:03.650 --> 00:02:05.800 datetime.datetime.now, 53 00:02:05.800 --> 00:02:08.650 and then we do the datetime objects method 54 00:02:08.650 --> 00:02:11.520 and then we grab the datetime object, such as today, 55 00:02:11.520 --> 00:02:16.040 and we do strftime, that's string format time. 56 00:02:16.040 --> 00:02:18.010 That's a method in the datetime object, 57 00:02:18.010 --> 00:02:21.130 and what we pass in is a string that uses 58 00:02:21.130 --> 00:02:23.290 the string formatting mini-language. 59 00:02:23.290 --> 00:02:25.027 For example, for the first one there, 60 00:02:25.027 --> 00:02:29.500 %Y means the year has four digits. 61 00:02:29.500 --> 00:02:32.513 And %m means the month has two digits. 62 00:02:32.513 --> 00:02:35.560 %d means the day has two digits. 63 00:02:35.560 --> 00:02:39.410 So that prints out "2019-12-23," for example. 64 00:02:39.410 --> 00:02:41.020 We've got a complete reference for 65 00:02:41.020 --> 00:02:44.910 the string format mini-language over at strftime.org. 66 00:02:44.910 --> 00:02:46.880 We've not written that, but it's really good. 67 00:02:46.880 --> 00:02:48.730 It has everything that you might possible need 68 00:02:48.730 --> 00:02:51.410 when working with these strings. 69 00:02:51.410 --> 00:02:53.830 In order to parse dates, for example, 70 00:02:53.830 --> 00:02:57.100 here we're asking the user for the current date, 71 00:02:57.100 --> 00:02:59.420 and we can assume they entered the day, 72 00:02:59.420 --> 00:03:01.300 then the month, then the year, 73 00:03:01.300 --> 00:03:05.590 you can then use the datetime class strptime 74 00:03:05.590 --> 00:03:08.050 for string parse time, 75 00:03:08.050 --> 00:03:11.470 to grab the string in the first argument 76 00:03:11.470 --> 00:03:15.490 and pass in the formatting string as the second argument 77 00:03:15.490 --> 00:03:17.630 and then the datetime object is going to be 78 00:03:17.630 --> 00:03:20.940 created for you using that information. 79 00:03:20.940 --> 00:03:24.530 Note that because we've got day, month, and year information 80 00:03:24.530 --> 00:03:26.840 in this string, when we parse it using 81 00:03:26.840 --> 00:03:31.340 %d, %m, %Y, what we end up getting is 82 00:03:31.340 --> 00:03:35.280 that datetime object, but without any time information, 83 00:03:35.280 --> 00:03:37.160 so that just defaults to midnight. 84 00:03:37.160 --> 00:03:39.860 If you wanted to put in hours and minutes and so forth 85 00:03:39.860 --> 00:03:42.660 you could use %h, for example, %m, 86 00:03:42.660 --> 00:03:44.300 and that would give you that. 87 00:03:44.300 --> 00:03:47.550 Again, more information at strftime.org. 88 00:03:47.550 --> 00:03:49.760 Let's take a look at what a timestamp is, 89 00:03:49.760 --> 00:03:52.270 and that is the number of seconds that have passed 90 00:03:52.270 --> 00:03:56.070 since the first of January 1970 at midnight. 91 00:03:56.070 --> 00:03:58.230 Why do we use the number of seconds? 92 00:03:58.230 --> 00:04:00.210 Well, simply because it's easier to work with. 93 00:04:00.210 --> 00:04:01.830 It's easier to work with a single number 94 00:04:01.830 --> 00:04:03.680 rather than many parts of the date like 95 00:04:03.680 --> 00:04:06.250 year, day, month, hour, et cetera. 96 00:04:06.250 --> 00:04:09.370 Datetime objects really have a method called timestamp 97 00:04:09.370 --> 00:04:12.280 that allows us to convert the datetime object 98 00:04:12.280 --> 00:04:14.810 that we are using over to a timestamp. 99 00:04:14.810 --> 00:04:16.560 So you can create the datetime object, 100 00:04:16.560 --> 00:04:19.160 for example with .now, and then convert 101 00:04:19.160 --> 00:04:21.240 to a timestamp with .timestamp. 102 00:04:21.240 --> 00:04:23.210 That is gonna give you a float 103 00:04:23.210 --> 00:04:25.490 that has the decimal place there 104 00:04:25.490 --> 00:04:27.090 for the number of microseconds 105 00:04:27.090 --> 00:04:30.130 because everything before the decimal place is just seconds. 106 00:04:30.130 --> 00:04:32.610 That's just some extra precision there 107 00:04:32.610 --> 00:04:33.900 that often we don't use, 108 00:04:33.900 --> 00:04:35.383 but you can use if you want. 109 00:04:36.470 --> 00:04:38.050 Thank you guys for joining me in this video. 110 00:04:38.050 --> 00:04:39.200 I hope you've learned something. 111 00:04:39.200 --> 00:04:40.723 I'll see you in the next one.