1 00:00:05,380 --> 00:00:09,050 so far we've been writing programs more or less largely contained every 2 00:00:09,050 --> 00:00:14,060 everything they need in a single Python file now there were a couple of 3 00:00:14,060 --> 00:00:18,180 exceptions when we imported random to make our guessing game more interesting and of 4 00:00:18,180 --> 00:00:21,880 course when we also imported shelve in the last section dealing with 5 00:00:21,880 --> 00:00:26,990 file input and output now the Python documentation refers to a file 6 00:00:26,990 --> 00:00:31,630 containing a Python program such as we've been creating as a script but that 7 00:00:31,630 --> 00:00:36,180 said it's also possible to produce Python code that is not intended to be 8 00:00:36,180 --> 00:00:41,050 executed directly instead to the provides functions classes and 9 00:00:41,050 --> 00:00:46,250 variable definitions etc that are designed to be used by other programs 10 00:00:46,250 --> 00:00:49,820 we managed to do quite a lot without importing modules into our scripts 11 00:00:49,820 --> 00:00:52,570 the part of power of Python 12 00:00:52,570 --> 00:00:57,050 is that it allows us to use modules to provide that extra functionality there's 13 00:00:57,050 --> 00:01:01,410 nothing to stop us from creating our own modules and will be looking how to this 14 00:01:01,410 --> 00:01:05,550 later in this section in order to use a module we have to import it into our program 15 00:01:05,550 --> 00:01:10,180 using the import command and of course you saw that in the last section this 16 00:01:10,180 --> 00:01:14,300 can take a couple of forms actually so let's have a play with the Python turtle 17 00:01:14,300 --> 00:01:19,740 module just to really understand how import works so create a new file 18 00:01:19,740 --> 00:01:22,030 and setup a new project 19 00:01:22,030 --> 00:01:28,940 create a new Python file and call it Turtledemo 20 00:01:28,940 --> 00:01:31,910 now the turtle module is based on the educational programming language from 21 00:01:31,910 --> 00:01:36,090 the late 1960's called logo and that allowed amongst other things children to 22 00:01:36,090 --> 00:01:40,600 control an on-screen turtle by giving it simple instructions to move and turn now 23 00:01:40,600 --> 00:01:45,140 there is a pen attached to this turtle so when it moves it draws a line behind itself to 24 00:01:45,140 --> 00:01:48,630 so let us type in a simple example that's gonna move the turtle around the screen 25 00:01:48,630 --> 00:01:56,100 gonna start with importing the module..... 26 00:01:56,100 --> 00:02:02,330 ....and we type a few commands first things first will type in the command to go forward so... 27 00:02:05,010 --> 00:02:10,020 ...we can get it turn right 250 degrees.... 28 00:02:10,020 --> 00:02:19,170 ......can try going getting it to go forward again..... 29 00:02:19,170 --> 00:02:26,600 ....so a simple example moves the turtle forward 30 00:02:26,600 --> 00:02:36,760 turns right 250 degrees and it moves forward again so run it and did you see what 31 00:02:36,760 --> 00:02:40,590 happened briefly you saw the command come up on the screen or little box come 32 00:02:40,590 --> 00:02:41,330 up on the screen, and you can see 33 00:02:41,330 --> 00:02:45,070 drawing something and then quickly close the program down and that's how it 34 00:02:45,070 --> 00:02:49,230 works because our program ended the graphic screen closed down so 35 00:02:49,230 --> 00:02:53,930 there is a good way to prevent this and we can import another module to do that called time so we can type... 36 00:02:53,930 --> 00:03:00,030 ...below the first import and then create another line of code on line 8..... 37 00:03:00,030 --> 00:03:06,460 we will get it to sleep for 4 seconds so we type time....which is getting to 38 00:03:06,460 --> 00:03:13,460 get to sleep before seconds so we should be able to see it now so run it again and you 39 00:03:13,460 --> 00:03:18,450 see what happen was that it went forward turned 250 degrees to the right and then 40 00:03:18,450 --> 00:03:22,480 continued on as you saw that it slept for 4 seconds giving us a time to see the 41 00:03:22,480 --> 00:03:26,550 turtles drawing on the screen before the program ended and it close it down now 42 00:03:26,550 --> 00:03:32,430 interestingly enough there's actually a bug in the IntelliJ product both IDEA and Pycharm 43 00:03:32,430 --> 00:03:37,110 and that causes them to display a warning about cannot find reference forward in turtle.py so 44 00:03:37,110 --> 00:03:41,930 if we hover this and have a I'll fix that part because it needs a blank line in the end 45 00:03:41,930 --> 00:03:49,180 here is the actual error itself you can see it saying it cannot find reference for two turtle.py and as you saw 46 00:03:49,180 --> 00:03:53,710 the program is fine so clearly not a problem with the code but IntelliJ can struggle 47 00:03:53,710 --> 00:03:58,150 with importing from some modules and noticed that importing the module from 48 00:03:58,150 --> 00:04:03,360 time using time module I should say using the the sleep method had no problems it found 49 00:04:03,360 --> 00:04:07,920 that ok so warnings are useful or will become less useful if they are incorrect because 50 00:04:07,920 --> 00:04:10,790 ultimately that can detract from the ones we should be paying attention to 51 00:04:10,790 --> 00:04:16,100 and start ignoring them all together so in this scenario where you convinced 52 00:04:16,100 --> 00:04:16,930 it's a warning 53 00:04:16,930 --> 00:04:20,459 that it is a bug where we're pretty sure that it's a bug here right now with 54 00:04:20,459 --> 00:04:25,360 IntelliJ we can suppress them so they can be safely ignored what we can do is 55 00:04:25,360 --> 00:04:30,080 do that and one way is on a statement by statement basis so come up here and add a new 56 00:04:30,080 --> 00:04:42,750 line for we can put a....... 57 00:04:42,750 --> 00:04:48,020 you can see what happens as soon as I finish typing that the a warning disappeared so that handles 58 00:04:48,020 --> 00:04:53,170 suppressing the error or the warning I should say just on a single line it would 59 00:04:53,170 --> 00:04:58,380 soon get annoying having to do that with each line to get rid of each warning message so what you can do is 60 00:04:58,380 --> 00:05:02,610 disable it for all future turtke commands which isprobably be wise in this 61 00:05:02,610 --> 00:05:03,420 case 62 00:05:03,420 --> 00:05:08,450 because we still got 2 warnings here to the right hand side so we come over here to line 6 click on 63 00:05:08,450 --> 00:05:15,440 right on line 6 see that little pop up comes up so we can select the pop up and use the third down here mark all 64 00:05:15,440 --> 00:05:20,710 unresolved attributes of turtle as ignored click on that you can see that 65 00:05:20,710 --> 00:05:24,780 then disappeared all the warnings and we got the green tick which means 66 00:05:24,780 --> 00:05:32,160 as far as IntelliJ is concern everything is ok so after doing that you could delete line 4 because the 67 00:05:32,160 --> 00:05:36,860 command on line 6 when we right clicked it overwrote that command anyway 68 00:05:37,440 --> 00:05:41,910 we have taken those warnings off let us just say for some reason IntelliJ fix that error 69 00:05:41,910 --> 00:05:45,960 and it's now something you want to put back on again you want to enable 70 00:05:45,960 --> 00:05:51,830 warnings again to do that it is on a file by file basis so you open the file you want to deal with come up here to 71 00:05:51,830 --> 00:05:56,730 code to analyze click on Config Current File 72 00:05:56,730 --> 00:05:58,040 Analysis 73 00:05:58,040 --> 00:06:02,080 click on configure inspections and what you need to do is you need to scroll 74 00:06:02,080 --> 00:06:05,570 down and there will be a list of all these other bits and pieces you want one that says Python 75 00:06:05,570 --> 00:06:09,790 and if there has been a change made you will notice it will be showing in blue it is showing 76 00:06:09,790 --> 00:06:12,720 in blue here because we have made that change so what I'm going to do is come down 77 00:06:12,720 --> 00:06:18,190 to unresolved references and that's showing in blue again and if we want 78 00:06:18,190 --> 00:06:21,920 to get rid of that you can see here the ignore references we can add some more here 79 00:06:21,920 --> 00:06:28,850 if we have some but otherwise we can click on it and click on minus to remove it and the warnings then come 80 00:06:28,850 --> 00:06:29,220 back 81 00:06:29,220 --> 00:06:34,790 and if we go back in to analyze again analyzed Config Current File Analysis 82 00:06:34,790 --> 00:06:36,880 configure inspections 83 00:06:36,880 --> 00:06:41,280 and looking back here now notice now its not in blue anymore and also come up here too 84 00:06:41,280 --> 00:06:45,570 Python that is no longer in blue either so that's a quick way to 85 00:06:45,570 --> 00:06:51,190 determine whether you actually made that any changes to this particular model or not 86 00:06:51,190 --> 00:06:55,170 so I'm gonna re add that again because it's just an annoying warning we do 87 00:06:55,170 --> 00:07:00,360 wanna get rid off so I'm gonna click on right here and select the 88 00:07:00,360 --> 00:07:07,920 pop up click on mark all unresolved attributes of turtle as ignored again and we get your green arrow back again 89 00:07:07,920 --> 00:07:13,320 so just running the app again so you can see we got our drawing sits there for a few seconds 90 00:07:13,320 --> 00:07:18,810 four seconds to be exact and closes down so the pause is a bit arbitrary so the correct way to 91 00:07:18,810 --> 00:07:23,480 give us time to view the reptilian artwork is to use the turtles module done 92 00:07:23,480 --> 00:07:27,450 method this also me so we can get rid of the time import so I'm going to 93 00:07:27,450 --> 00:07:36,890 delete the time import and instead of time.sleep we are gonna put.... 94 00:07:36,890 --> 00:07:37,450 essentially now 95 00:07:37,450 --> 00:07:42,730 the masterpiece is going to stay there until we close the window so we just sit here for a few seconds 96 00:07:42,730 --> 00:07:45,630 to make sure you can see nothing's happening so we literally had to come 97 00:07:45,630 --> 00:07:49,230 over here and close it down for that change to take effect and for our program to 98 00:07:49,230 --> 00:07:54,080 exit the other thing to remember was with using the import command to import 99 00:07:54,080 --> 00:07:57,640 the turtle module we can then use all the objects it provides by prefixing 100 00:07:57,640 --> 00:08:02,260 them with turtle and a dot so turtle.forward as you saw turtle.right etc 101 00:08:02,260 --> 00:08:08,200 because we also saw that with time.sleep until I just remove the code there now there is another way to import 102 00:08:08,200 --> 00:08:12,310 from a module specifying just things we want to import as supposed to doing an 103 00:08:12,310 --> 00:08:16,260 import of everything and what I mean by that is I'm going to delete that line on the 104 00:08:16,260 --> 00:08:19,360 first line the import and we could do something like this instead of we can be 105 00:08:19,360 --> 00:08:28,200 more selective we can say from....so we are only going 106 00:08:28,200 --> 00:08:33,480 to import the first method called for and then by doing that I can get rid of 107 00:08:33,480 --> 00:08:38,630 this turtle. at the start and notice how it has found forward because its found and look for it 108 00:08:38,630 --> 00:08:42,559 in the turtle module so again essentially what we're doing is we're telling Python to import 109 00:08:42,559 --> 00:08:46,130 just the forward method from turtle and doing it this way means that we don't 110 00:08:46,130 --> 00:08:50,090 have to keep prefixing forward with turtle. all the time and if we run 111 00:08:50,090 --> 00:08:56,580 this we do get some errors and the errors on lines for 4 5 and 7 saying that 112 00:08:56,580 --> 00:09:03,720 turtle is not defined but we could fix it if we wanted to by changing our import on line 1 putting a... 113 00:09:03,720 --> 00:09:08,650 for the right method and done for the right one as well and if we run that again we should find it 114 00:09:08,650 --> 00:09:16,180 works fine and sorry had to get rid of the turtle. before our commands and 115 00:09:16,180 --> 00:09:20,400 notice how these are all enabled now so it has found those now if I run it we find that it works 116 00:09:20,400 --> 00:09:25,780 quite nicely and we only imported those functions from the 117 00:09:25,780 --> 00:09:30,630 turtle module that we actually need to so close it down so doing it this way can be useful for 118 00:09:30,630 --> 00:09:34,090 using a particular object a lot in the program but the problem is it only 119 00:09:34,090 --> 00:09:37,670 import things that are specifically listed on the import line and as you saw 120 00:09:37,670 --> 00:09:41,900 those errors until I remove them the other ones aren't available so what I can't do now is to do something 121 00:09:41,900 --> 00:09:43,210 like.... 122 00:09:43,210 --> 00:09:47,010 ....which is a valid command 123 00:09:47,010 --> 00:09:53,010 if we run that now that is not going to work, unnamed turtle was not to defined because again for that reason we 124 00:09:53,010 --> 00:09:57,020 only specified the specific things we wanted and we don't need to specify turtle. 125 00:09:57,020 --> 00:10:01,050 and in actual fact turtle. doesn't work because as far as Python is concerned that 126 00:10:01,050 --> 00:10:09,320 module doesn't exist and the other things we can't do either is type...try to run that...we get the error 127 00:10:09,320 --> 00:10:16,390 turtle circle and if I comment this line and run it again we name circle is not 128 00:10:16,390 --> 00:10:20,140 defined as well that's because we haven't specified circle up here on line 129 00:10:20,140 --> 00:10:25,770 1 so if wanted circle. to work I'll delete line 7 because we know how to do that we 130 00:10:25,770 --> 00:10:30,940 could just add circle up here on line 1 to fix that after the comma but if want to get line 5 131 00:10:30,940 --> 00:10:35,450 to to work like this what we can do is below the from turtle command we can 132 00:10:35,450 --> 00:10:48,050 also put an import....so we should find if we run it now everything works fine 133 00:10:48,050 --> 00:10:52,860 and you can see we got a different result there we got a circle created and then we went on and plotted 134 00:10:52,860 --> 00:10:58,990 or started plotting the triangle so that's good so that works fine 135 00:10:58,990 --> 00:11:02,380 so this does demonstrate the two different ways an import can be used and the effect each 136 00:11:02,380 --> 00:11:06,780 it has on how you can use the imported objects generally speaking you wouldn't 137 00:11:06,780 --> 00:11:09,130 want to mix methods with the same module so 138 00:11:09,130 --> 00:11:12,140 in our example what you wanna do import turtle 139 00:11:12,140 --> 00:11:16,890 on line 2 you don't only just have an import turtle like on line 2 or you import the existing 140 00:11:16,890 --> 00:11:21,490 individual methods class variables and variables but rarely combined both 141 00:11:21,490 --> 00:11:25,630 because obviously that can lead to confusing code especially because turtle 142 00:11:25,630 --> 00:11:29,110 .forward would also work as well as forward now and that could be quite 143 00:11:29,110 --> 00:11:32,820 confusing to someone reading your code and wondering why things are different and 144 00:11:32,820 --> 00:11:37,560 why you've done things sort of both ways so it is good to choose one way or the other now there is one way 145 00:11:37,560 --> 00:11:40,840 to use import that's definitely not recommended 146 00:11:40,840 --> 00:11:44,110 so it's possible to import everything or more actually almost everything from the 147 00:11:44,110 --> 00:11:46,140 module using import star 148 00:11:46,140 --> 00:11:52,490 so we could do something like here change our references here from turtle import I put import * and get rid of this 149 00:11:52,490 --> 00:12:00,760 import turtle on line 2 and I've got to delete line 5 as well so we are left with our commands and i'll put the circle 150 00:12:00,760 --> 00:12:13,510 command back.....so we should be able to run that so you can see that work ok and depending on 151 00:12:13,510 --> 00:12:18,240 your operating system you may get some errors here in my case i didn't get any 152 00:12:18,240 --> 00:12:22,180 errors and there was a tick their but IntelliJ may struggle when underlining the 153 00:12:22,180 --> 00:12:27,400 method calls in red but as you saw the program will still totally run anyway although you 154 00:12:27,400 --> 00:12:31,520 can import from a module in this way with a star which will import everything 155 00:12:31,520 --> 00:12:35,770 who's name does not start with an underscore doing so is frowned upon it's 156 00:12:35,770 --> 00:12:39,810 very useful to save typing when using an interactive session in idle for example 157 00:12:39,810 --> 00:12:43,330 but other than that you should really avoid this way of importing now one 158 00:12:43,330 --> 00:12:47,190 reason for that or you don't want to do that is that you actually have no idea what 159 00:12:47,190 --> 00:12:51,770 is being imported so an imported name can hid one of your objects or you can hide 160 00:12:51,770 --> 00:12:55,760 one of the imported names that you need and just to give you an idea that 161 00:12:55,760 --> 00:12:59,550 in this example we got to demonstrate why this could be a problem 162 00:12:59,550 --> 00:13:03,270 so lets just say we're going to use the import start so what I'm going to do is put 163 00:13:03,270 --> 00:13:15,030 something on line 1 ill put.....and we got our from turtle 164 00:13:15,030 --> 00:13:18,200 import.... 165 00:13:18,200 --> 00:13:29,650 on line 3 we got our import I come to line 10 we have our done and we wanna do....so if we run this 166 00:13:29,650 --> 00:13:34,840 we get a picture drawing just fine nothing happens until we close down but once we 167 00:13:34,840 --> 00:13:38,750 do closed and you can see that we you get the message printed is a 168 00:13:38,750 --> 00:13:44,810 function address of the turtle done method and not the string message Well 169 00:13:44,810 --> 00:13:49,560 done you have finished your drawing like you would expect so that could be confusing but if we did it the other way as 170 00:13:49,560 --> 00:13:59,120 well things could get even a little bit worse so if we put the import on line 1 and change them around 171 00:13:59,120 --> 00:14:03,520 so literally just changed lines 1 and 3 around and done nothing else if we 172 00:14:03,520 --> 00:14:11,000 run this again it will work it will draw the picture or starts to but then there's actually a 173 00:14:11,000 --> 00:14:15,470 problem and the problem is when it reaches the done line which is on line 174 00:14:15,470 --> 00:14:19,450 10 and it says string object is not callable so what's happening of course 175 00:14:19,450 --> 00:14:25,150 is its trying to call or to treat the string as a method and executing it rather than 176 00:14:25,150 --> 00:14:29,270 using the done method from the turtle import now of course this second 177 00:14:29,270 --> 00:14:33,390 example in particular but also the first one before I swap them over are really quite 178 00:14:33,390 --> 00:14:37,190 contrived because we called the done method with only a few lines defining the 179 00:14:37,190 --> 00:14:40,560 string variable so that would be very hard to miss the fact that something 180 00:14:40,560 --> 00:14:44,280 wasn't right ordinarily but however if you consider a program with hundreds of 181 00:14:44,280 --> 00:14:49,190 lines of code mistakes like this would be much easier to make and harder to find so 182 00:14:49,190 --> 00:14:53,370 bottom line here is that unless you're working in an interactive session do not 183 00:14:53,370 --> 00:14:58,490 do an import star so I'm gonna finish the video here now and in the next video 184 00:14:58,490 --> 00:15:02,570 we are gonna start talking about the Python Standard library so see you in that video