1 00:00:05,260 --> 00:00:06,550 All right, so as I mentioned 2 00:00:06,550 --> 00:00:08,340 towards the end of the last video, 3 00:00:08,340 --> 00:00:10,470 there's a slight problem with this code 4 00:00:10,470 --> 00:00:13,120 and I'm gonna get you to look at a challenge 5 00:00:13,120 --> 00:00:14,950 of fixing that shortly, 6 00:00:14,950 --> 00:00:18,610 but before we do that, let's see what the actual problem is. 7 00:00:18,610 --> 00:00:20,950 So what happens if the calling code specifies 8 00:00:20,950 --> 00:00:24,910 a key word argument that our function is already using? 9 00:00:24,910 --> 00:00:27,990 So in our code, we need to suppress the end of line 10 00:00:27,990 --> 00:00:31,450 character when we call the built in print function. 11 00:00:31,450 --> 00:00:33,070 So we're parsing, as you can see here, 12 00:00:33,070 --> 00:00:36,400 the end equals on line four with the little space there 13 00:00:36,400 --> 00:00:38,660 and I'm going to actually show you, 14 00:00:38,660 --> 00:00:41,170 I'm gonna change the calling code on line seven 15 00:00:41,170 --> 00:00:44,080 to put to also specify the end argument, 16 00:00:44,080 --> 00:00:46,220 which would be something that ordinarily 17 00:00:46,220 --> 00:00:48,390 would be a perfectly valid thing to do. 18 00:00:48,390 --> 00:00:51,440 So if I change that and put end= 19 00:00:51,440 --> 00:00:54,350 single quotes, a new line character. 20 00:00:54,350 --> 00:00:56,930 So if we actually run this now. 21 00:00:59,520 --> 00:01:01,040 So what's happening here is you can see 22 00:01:01,040 --> 00:01:04,349 there's an error is that kwargs contains the end argument. 23 00:01:04,349 --> 00:01:07,410 You can see that I'm calling that there. 24 00:01:07,410 --> 00:01:10,630 You can see that's showing in the printout of kwargs 25 00:01:10,630 --> 00:01:13,710 that we're doing on line two in the console output. 26 00:01:13,710 --> 00:01:15,850 But then we're also providing a value for it 27 00:01:15,850 --> 00:01:17,440 here on line four. 28 00:01:17,440 --> 00:01:20,350 You can't actually specify the same key word twice, 29 00:01:20,350 --> 00:01:22,050 and that's the problem. 30 00:01:22,050 --> 00:01:24,850 The specific error, got multiple valleys 31 00:01:24,850 --> 00:01:26,900 for key word argument end. 32 00:01:26,900 --> 00:01:29,180 And consequently we're getting a crash for that. 33 00:01:29,180 --> 00:01:31,140 Alright, so there's two ways to deal with this 34 00:01:31,140 --> 00:01:35,320 and I'm gonna show both in your solution to the challenge. 35 00:01:35,320 --> 00:01:37,820 Okay, but onto your challenge. 36 00:01:40,420 --> 00:01:44,320 You need to look at and fix the print_backwards function 37 00:01:44,320 --> 00:01:47,990 so that it correctly handles the case when the calling code 38 00:01:47,990 --> 00:01:51,190 also specifies the end keyword argument. 39 00:01:51,190 --> 00:01:52,790 And just as a tip here, you may want to remove 40 00:01:52,790 --> 00:01:55,760 the file=backwards from the call to print_backwards, 41 00:01:55,760 --> 00:01:57,760 just so you don't have to keep opening the file 42 00:01:57,760 --> 00:01:58,870 to check the results. 43 00:01:58,870 --> 00:02:01,290 Instead, getting the output on the screen. 44 00:02:01,290 --> 00:02:03,320 So that's your challenge, see how you go with it. 45 00:02:03,320 --> 00:02:07,530 Pause the video and I'll see you when you get back. 46 00:02:07,530 --> 00:02:08,970 Okay, so how did you get on? 47 00:02:08,970 --> 00:02:10,970 Hopefully you managed to solve that. 48 00:02:10,970 --> 00:02:13,620 And as I mentioned, there's actually two solutions to this, 49 00:02:13,620 --> 00:02:17,780 or two ways to deal with it, and I'm gonna show you both. 50 00:02:17,780 --> 00:02:20,710 Both of the solutions rely on making sure 51 00:02:20,710 --> 00:02:24,830 that we don't parse the end key word argument in kwargs. 52 00:02:24,830 --> 00:02:27,650 One approach is to actually include end 53 00:02:27,650 --> 00:02:29,390 in our parameter list. 54 00:02:29,390 --> 00:02:32,470 If we come up here and after the *args 55 00:02:32,470 --> 00:02:34,490 and before the **kwargs, 56 00:02:34,490 --> 00:02:38,450 we can actually put end= and then our space 57 00:02:38,450 --> 00:02:41,990 in single quotes and then a comma and a space 58 00:02:41,990 --> 00:02:43,820 and then our **kwargs. 59 00:02:45,410 --> 00:02:49,650 Just like with *args, **kwargs will actually scoop up 60 00:02:49,650 --> 00:02:51,830 any remaining key word arguments 61 00:02:51,830 --> 00:02:55,200 that we don't specify in our function definition. 62 00:02:55,200 --> 00:02:57,060 So that's the reason that I'm putting the end= 63 00:02:57,060 --> 00:02:58,600 a bit prior to that. 64 00:02:58,600 --> 00:03:01,220 Now, there is a slight difference though. 65 00:03:01,220 --> 00:03:03,630 *args deals with positional arguments. 66 00:03:03,630 --> 00:03:04,710 If they don't have names, 67 00:03:04,710 --> 00:03:07,310 so they just appear in order in the function call. 68 00:03:07,310 --> 00:03:10,220 But **kwargs uses the parameter names, 69 00:03:10,220 --> 00:03:12,630 so it doesn't care what order we specify them in 70 00:03:12,630 --> 00:03:14,400 when calling the function. 71 00:03:14,400 --> 00:03:17,210 It just scoops up any that our function hasn't declared 72 00:03:17,210 --> 00:03:19,350 and puts them into kwargs. 73 00:03:19,350 --> 00:03:21,330 So before running the programme, 74 00:03:21,330 --> 00:03:23,960 I'm gonna remove the file=backwards argument 75 00:03:23,960 --> 00:03:27,380 just so we can see the results on screen. 76 00:03:30,150 --> 00:03:32,720 So we'll try running that now. 77 00:03:32,720 --> 00:03:34,790 Alright, so that's the first option. 78 00:03:34,790 --> 00:03:36,210 That works fine, as you can see there. 79 00:03:36,210 --> 00:03:38,070 There's now no errors showing. 80 00:03:38,070 --> 00:03:39,630 The other approach though is to remove any 81 00:03:39,630 --> 00:03:42,380 end key word argument from the kwargs dictionary 82 00:03:42,380 --> 00:03:45,380 before parsing it on to the built in print function. 83 00:03:45,380 --> 00:03:47,270 I'm gonna leave that first statement definition 84 00:03:47,270 --> 00:03:49,600 commented out for reference. 85 00:03:51,090 --> 00:03:54,260 So I'll take a copy of that, paste it. 86 00:03:55,450 --> 00:03:57,240 And I'll comment out the first one. 87 00:03:57,240 --> 00:03:58,740 So I'm gonna change this, 88 00:03:58,740 --> 00:04:00,850 and we're gonna come down here to, 89 00:04:00,850 --> 00:04:03,010 after we do the print of kwargs, 90 00:04:03,010 --> 00:04:06,510 we're going to do kwr, so kwargs, dot pop, 91 00:04:09,110 --> 00:04:13,270 single quotes, end, comma, space, none with a capital N. 92 00:04:15,220 --> 00:04:16,420 So kwargs is just a dictionary, 93 00:04:16,420 --> 00:04:18,180 so we're free to manipulate its contents 94 00:04:18,180 --> 00:04:20,350 just like any other dictionary. 95 00:04:20,350 --> 00:04:22,860 I've used the dictionary pop method here. 96 00:04:22,860 --> 00:04:26,830 Now, if we click on pop and have a look at that, 97 00:04:26,830 --> 00:04:28,270 you can see that it removes 98 00:04:28,270 --> 00:04:30,400 the specified key from the dictionary. 99 00:04:30,400 --> 00:04:33,570 And we're providing the default value of none 100 00:04:33,570 --> 00:04:36,960 to prevent an error if end isn't already in the dictionary. 101 00:04:36,960 --> 00:04:40,530 Now, we could use other methods for removing the key, 102 00:04:40,530 --> 00:04:41,970 such as the del command, 103 00:04:41,970 --> 00:04:44,740 but just remember that the end argument may not exist, 104 00:04:44,740 --> 00:04:47,400 so your code has to check it before removing it 105 00:04:47,400 --> 00:04:49,710 or catch the key error exception. 106 00:04:49,710 --> 00:04:53,250 Alright, so we'll go back and check this code. 107 00:04:53,250 --> 00:04:54,080 And run. 108 00:04:56,260 --> 00:05:00,100 We can see that it too is also working just fine. 109 00:05:00,100 --> 00:05:01,860 Alright, so if you use one of those approaches 110 00:05:01,860 --> 00:05:03,910 to solving the challenge, then well done. 111 00:05:03,910 --> 00:05:05,770 And if you found another approach that also works, 112 00:05:05,770 --> 00:05:06,730 please let us know. 113 00:05:06,730 --> 00:05:08,140 That'd be very interesting. 114 00:05:08,140 --> 00:05:10,250 Alright, so that challenge was intended to show you 115 00:05:10,250 --> 00:05:12,310 how you can manipulate kwargs, 116 00:05:12,310 --> 00:05:15,100 either by providing the key word in your own definition 117 00:05:15,100 --> 00:05:18,280 or explicitly removing it from the dictionary. 118 00:05:18,280 --> 00:05:21,030 Now, our print_backwards function at the moment 119 00:05:21,030 --> 00:05:24,630 doesn't really behave like the built in print function. 120 00:05:24,630 --> 00:05:26,460 We've got working code, but it doesn't behave 121 00:05:26,460 --> 00:05:29,400 in the way that the calling code would expect. 122 00:05:29,400 --> 00:05:31,350 So to see what I mean there, 123 00:05:31,350 --> 00:05:33,090 let's press another string immediately 124 00:05:33,090 --> 00:05:35,670 after the print_backwards call. 125 00:05:37,270 --> 00:05:40,440 We'll just do a print, another string. 126 00:05:41,460 --> 00:05:43,730 And if we actually run that, 127 00:05:43,730 --> 00:05:45,620 you can see we've got another string 128 00:05:45,620 --> 00:05:47,840 sort of showing on the same line, 129 00:05:47,840 --> 00:05:49,360 right at the end of our backward string 130 00:05:49,360 --> 00:05:51,190 instead of on a new line. 131 00:05:51,190 --> 00:05:55,150 We're effectively using the end argument as a separator. 132 00:05:55,150 --> 00:05:57,560 Because we're using multiple calls to the built in 133 00:05:57,560 --> 00:05:59,660 print function inside our loop, 134 00:05:59,660 --> 00:06:02,290 we have to use end to prevent each word 135 00:06:02,290 --> 00:06:04,030 appearing on a new line. 136 00:06:04,030 --> 00:06:06,040 Now if we specify sep when calling 137 00:06:06,040 --> 00:06:09,860 our print_backwards function, it actually won't do anything. 138 00:06:09,860 --> 00:06:12,140 So let's compare our code to the built in one, 139 00:06:12,140 --> 00:06:14,980 when a separator's used in the function call. 140 00:06:14,980 --> 00:06:17,420 I'm gonna add this code outside the file loop 141 00:06:17,420 --> 00:06:20,620 and print a blank line first to separate the output. 142 00:06:20,620 --> 00:06:24,350 So let's have a go at doing that down here. 143 00:06:24,350 --> 00:06:26,950 So we're gonna do print to move to a new line 144 00:06:26,950 --> 00:06:29,180 before we start and then print, 145 00:06:29,180 --> 00:06:30,620 and I might take a copy of this again, 146 00:06:30,620 --> 00:06:32,790 just to save us typing it. 147 00:06:35,410 --> 00:06:38,000 We're gonna leave the end in there like so, 148 00:06:38,000 --> 00:06:40,110 but then we're also gonna introduce the sep, 149 00:06:40,110 --> 00:06:43,270 so sep= and we're going to use a pipe character, 150 00:06:43,270 --> 00:06:46,220 and then we're going to come up here 151 00:06:46,220 --> 00:06:48,450 and do an equivalent thing, 152 00:06:48,450 --> 00:06:51,630 but I'm going to just call the print function. 153 00:06:51,630 --> 00:06:54,890 So print in this case, exactly the same as the call 154 00:06:54,890 --> 00:06:56,870 on the line below to print_backwards, 155 00:06:56,870 --> 00:07:00,870 but we're just calling the print function instead. 156 00:07:00,870 --> 00:07:03,710 And let's just try running it now. 157 00:07:04,730 --> 00:07:07,390 So you can see in the version, the print version, 158 00:07:07,390 --> 00:07:10,230 we've got the pipe character working quite nicely. 159 00:07:10,230 --> 00:07:12,830 It's between each word, but on our version, 160 00:07:12,830 --> 00:07:16,070 the version that's calling the print_backwards function, 161 00:07:16,070 --> 00:07:18,990 the separator, the pipe character, isn't working. 162 00:07:18,990 --> 00:07:21,550 We've still got the space only working. 163 00:07:21,550 --> 00:07:22,830 So the point I wanna make here is that 164 00:07:22,830 --> 00:07:25,820 kwargs is very useful, but you also have to be careful 165 00:07:25,820 --> 00:07:27,790 that you don't subvert the meaning of the arguments 166 00:07:27,790 --> 00:07:29,590 that you're parsing on. 167 00:07:29,590 --> 00:07:31,280 Now we could fix this by joining the reverse 168 00:07:31,280 --> 00:07:34,090 words up into a string and using a single call 169 00:07:34,090 --> 00:07:36,330 to built in print function. 170 00:07:36,330 --> 00:07:38,730 In fact, that's probably the way I'd recommend it. 171 00:07:38,730 --> 00:07:40,450 The code would end up being a lot cleaner 172 00:07:40,450 --> 00:07:43,360 and more obvious with what's going on. 173 00:07:43,360 --> 00:07:45,910 But this video is about using args and kwargs, 174 00:07:45,910 --> 00:07:49,430 so I'm going to manipulate the key word arguments instead. 175 00:07:49,430 --> 00:07:51,220 You may find yourself having to do this 176 00:07:51,220 --> 00:07:52,930 when subclassing another class, 177 00:07:52,930 --> 00:07:55,400 so it's also useful to see how to do it. 178 00:07:55,400 --> 00:07:57,890 But what we're going to do is use any sep argument 179 00:07:57,890 --> 00:08:01,540 that the calling code provides instead of hard coding end 180 00:08:01,540 --> 00:08:05,610 to be a space, which it's currently doing on line six. 181 00:08:05,610 --> 00:08:07,780 So you can see it's hard coding the end there. 182 00:08:07,780 --> 00:08:09,960 And once we've done that, we'll add a final print call 183 00:08:09,960 --> 00:08:12,500 using whatever end value has been provided. 184 00:08:12,500 --> 00:08:15,060 Now I'm gonna copy the print_backwards function 185 00:08:15,060 --> 00:08:17,450 and comment out the original so the code is still available 186 00:08:17,450 --> 00:08:20,340 in the resources section of this video. 187 00:08:20,340 --> 00:08:21,840 So let me do that. 188 00:08:23,810 --> 00:08:25,770 Copy that and then we'll comment that out 189 00:08:25,770 --> 00:08:28,520 and then come down here and we'll paste it in again 190 00:08:28,520 --> 00:08:31,750 and then we'll make the changes to that. 191 00:08:31,750 --> 00:08:34,750 And two lines there to keep the editor happy. 192 00:08:34,750 --> 00:08:36,190 Alright, so firstly, what we're going to do 193 00:08:36,190 --> 00:08:37,990 is delete these two lines here, 194 00:08:37,990 --> 00:08:40,929 the print kwargs and the kwargs.pop 195 00:08:40,929 --> 00:08:43,049 and then we wanna add something. 196 00:08:43,049 --> 00:08:47,250 After here, we're going to then add end_character 197 00:08:47,250 --> 00:08:51,000 is equal to kwargs.pop end, then the slash N, 198 00:08:57,390 --> 00:09:00,350 single quotes, and then set_character 199 00:09:00,350 --> 00:09:03,600 is equal to kwargs.pop, and that's sep, 200 00:09:07,450 --> 00:09:09,370 and then a space in single quotes. 201 00:09:09,370 --> 00:09:12,430 And then we're gonna come down to our call to print here. 202 00:09:12,430 --> 00:09:15,750 We're gonna change end= and single quote and space 203 00:09:15,750 --> 00:09:17,770 that was in there, we're gonna change 204 00:09:17,770 --> 00:09:20,270 that instead to sep_character. 205 00:09:22,610 --> 00:09:25,330 They're still needing **kwargs on the end of that, 206 00:09:25,330 --> 00:09:26,660 and then on the line after that 207 00:09:26,660 --> 00:09:28,280 we're going to do a print. 208 00:09:28,280 --> 00:09:29,800 That's going to be after the (mumbling) is finished, 209 00:09:29,800 --> 00:09:32,630 so print, end= end_character. 210 00:09:37,340 --> 00:09:40,260 Alright, so let's just try running that. 211 00:09:40,260 --> 00:09:43,700 You can see now it's actually looking a lot better. 212 00:09:43,700 --> 00:09:45,370 It's now behaving almost the same as 213 00:09:45,370 --> 00:09:47,220 the built in print function. 214 00:09:47,220 --> 00:09:50,140 And it also works if we suppress the end of line character. 215 00:09:50,140 --> 00:09:53,390 Let's have a go at doing that just to see if it works. 216 00:09:53,390 --> 00:09:56,370 So first thing we're going to do here in this first print 217 00:09:56,370 --> 00:09:59,270 is we're going to change the end= 218 00:09:59,270 --> 00:10:01,300 and we're gonna remove the new line 219 00:10:01,300 --> 00:10:03,860 so it's just two single quotes. 220 00:10:03,860 --> 00:10:07,800 And we're also gonna do that on the regular or the, 221 00:10:07,800 --> 00:10:09,280 call to our method as well, 222 00:10:09,280 --> 00:10:12,130 so both the print and the call to our method. 223 00:10:12,130 --> 00:10:13,480 And actually what we'll do is we'll also change 224 00:10:13,480 --> 00:10:17,650 the separator this time to a /n for new line, **/n 225 00:10:20,460 --> 00:10:22,960 and we'll do the same for the function call 226 00:10:22,960 --> 00:10:27,130 to print_backwards, so separator= /n **/n. 227 00:10:28,700 --> 00:10:30,590 And then just to make it clear, 228 00:10:30,590 --> 00:10:34,760 we'll add a bit of text to separate it, so print= times 10. 229 00:10:38,500 --> 00:10:40,500 Right, so we're on that. 230 00:10:45,500 --> 00:10:47,910 So now the first word of our backward string starts 231 00:10:47,910 --> 00:10:51,060 on the same line as the last word on the print function. 232 00:10:51,060 --> 00:10:54,530 I've got the equals printout showing as the, 233 00:10:54,530 --> 00:10:57,720 well, after rather, the last backwards word. 234 00:10:57,720 --> 00:10:59,870 Looking at that, this is the code here 235 00:10:59,870 --> 00:11:01,430 that I'm talking about or the output. 236 00:11:01,430 --> 00:11:02,970 So the first word of our backwards string 237 00:11:02,970 --> 00:11:04,970 starts on the same line as the last word 238 00:11:04,970 --> 00:11:06,150 from the print function. 239 00:11:06,150 --> 00:11:07,820 That's the point really there. 240 00:11:07,820 --> 00:11:09,400 But then the line of equals 241 00:11:09,400 --> 00:11:11,720 does appear after our last backwards word, 242 00:11:11,720 --> 00:11:14,610 so print is correctly honouring the end of line characters 243 00:11:14,610 --> 00:11:17,840 but our print character, our print_backwards function 244 00:11:17,840 --> 00:11:19,550 doesn't cope when the end of line 245 00:11:19,550 --> 00:11:21,830 is suppressed, in this case. 246 00:11:21,830 --> 00:11:23,700 So as you can see, if you change the meaning 247 00:11:23,700 --> 00:11:27,010 of a key word argument, things can get a bit tricky. 248 00:11:27,010 --> 00:11:28,920 Now I probably wouldn't code this function 249 00:11:28,920 --> 00:11:30,650 using repeated calls to print. 250 00:11:30,650 --> 00:11:33,070 It's easier to join the backwards words 251 00:11:33,070 --> 00:11:35,590 using the join method that we've used before, 252 00:11:35,590 --> 00:11:38,650 then just call print once to print out the final string. 253 00:11:38,650 --> 00:11:40,890 But I can't leave you with an always working function 254 00:11:40,890 --> 00:11:43,380 so I'm gonna fix this one before ending the video. 255 00:11:43,380 --> 00:11:44,750 What we need to do though is handle 256 00:11:44,750 --> 00:11:47,640 the last word that we print a bit differently, 257 00:11:47,640 --> 00:11:49,490 so in fact it goes to a new line. 258 00:11:49,490 --> 00:11:51,060 The last word should be printed using 259 00:11:51,060 --> 00:11:54,500 the specified end argument rather than a separator. 260 00:11:54,500 --> 00:11:57,410 Now that's actually easier to do in Python. 261 00:11:57,410 --> 00:12:00,380 We just alter the range so that it reads the word backwards 262 00:12:00,380 --> 00:12:02,640 but stops before it prints the last one, 263 00:12:02,640 --> 00:12:04,330 which in this case is the first one 264 00:12:04,330 --> 00:12:05,950 because we're going backwards. 265 00:12:05,950 --> 00:12:08,890 Then we print the first word in args separately 266 00:12:08,890 --> 00:12:12,810 using the end value that the calling code specified. 267 00:12:12,810 --> 00:12:15,030 So let's have a look and see how to do that. 268 00:12:15,030 --> 00:12:17,350 Back to our definition here. 269 00:12:17,350 --> 00:12:18,970 The first that we've gotta do is change this 270 00:12:18,970 --> 00:12:20,430 full word in args. 271 00:12:20,430 --> 00:12:22,790 At the moment we've got ::-1. 272 00:12:22,790 --> 00:12:24,680 What we're gonna do, as I mentioned there, 273 00:12:24,680 --> 00:12:26,880 about changing the range, so we're gonna change 274 00:12:26,880 --> 00:12:28,710 that to, I'd be :0:-1. 275 00:12:35,580 --> 00:12:39,750 And then we're going to leave this coding as is on line 13. 276 00:12:40,680 --> 00:12:43,320 And then we're gonna come down here to the end here, 277 00:12:43,320 --> 00:12:45,440 print, and we're going to actually change that, 278 00:12:45,440 --> 00:12:47,510 so that we're gonna do a print. 279 00:12:47,510 --> 00:12:49,330 We'll actually comment that out, (mumbling) 280 00:12:49,330 --> 00:12:52,220 what it was before we're making this change. 281 00:12:52,220 --> 00:12:55,140 We're gonna do a print, args, zero, 282 00:12:57,660 --> 00:13:01,760 in square brackets, then another left square bracket, ::-1 283 00:13:01,760 --> 00:13:05,610 and then right square bracket, comma, end= 284 00:13:05,610 --> 00:13:08,690 and it's end_character then **kwargs. 285 00:13:11,390 --> 00:13:12,230 What we're doing here is effectively, we're uh, 286 00:13:12,230 --> 00:13:15,310 then print the first word separately. 287 00:13:20,630 --> 00:13:24,800 And by the way, as a result of that, that means... 288 00:13:29,640 --> 00:13:31,640 I'm gonna take a bit of a comment here, 289 00:13:31,640 --> 00:13:32,660 make it clear what we're doing, 290 00:13:32,660 --> 00:13:35,990 and here what we were doing on course was change the range. 291 00:13:35,990 --> 00:13:38,280 So those comments are meant to be read altogether. 292 00:13:38,280 --> 00:13:39,180 So I've changed the range, 293 00:13:39,180 --> 00:13:40,670 and print the first word separately 294 00:13:40,670 --> 00:13:42,300 which means we don't need this line, 295 00:13:42,300 --> 00:13:44,520 so that's why I've commented that out. 296 00:13:44,520 --> 00:13:46,360 Alright, so let's try running that. 297 00:13:46,360 --> 00:13:49,120 And the other thing I should have done previously 298 00:13:49,120 --> 00:13:53,200 was also remove this so I'm going to do that now. 299 00:13:54,480 --> 00:13:56,230 We'll run this again. 300 00:13:57,150 --> 00:13:58,760 That's actually what I was trying to do, 301 00:13:58,760 --> 00:14:01,600 because obviously we changed our functionality 302 00:14:01,600 --> 00:14:04,140 so we weren't using end anymore and I've removed that now 303 00:14:04,140 --> 00:14:07,230 and this is what was actually meant to happen. 304 00:14:07,230 --> 00:14:10,350 You can now see the equals sign is peering on the same line 305 00:14:10,350 --> 00:14:13,820 as our hollow going backwards (mumbling). 306 00:14:13,820 --> 00:14:17,640 So I used zero as the stock value in the code on line 12, 307 00:14:17,640 --> 00:14:18,750 as you can see here. 308 00:14:18,750 --> 00:14:21,140 Remember that the slides will extend up to 309 00:14:21,140 --> 00:14:23,000 but not including the stock value 310 00:14:23,000 --> 00:14:25,800 so therefore the first word isn't included. 311 00:14:25,800 --> 00:14:27,940 I'm gonna leave you to rerun the previous tests 312 00:14:27,940 --> 00:14:29,830 to confirm that our function now behaves 313 00:14:29,830 --> 00:14:31,950 the same as the built in print 314 00:14:31,950 --> 00:14:34,950 with different values for end and sep. 315 00:14:34,950 --> 00:14:37,180 So we can create new functions that are called 316 00:14:37,180 --> 00:14:39,950 in exactly the same way as an existing function 317 00:14:39,950 --> 00:14:43,010 but then change the way that the original function works. 318 00:14:43,010 --> 00:14:45,080 And we do this by retrieving the arguments 319 00:14:45,080 --> 00:14:49,080 using args, or using *args, I should say, and **kwargs 320 00:14:49,080 --> 00:14:52,640 to provide a version of the function of different behaviour. 321 00:14:52,640 --> 00:14:56,160 We can do the same thing with classes to create a subclass 322 00:14:56,160 --> 00:14:59,150 that adds additional functionality to the bass class 323 00:14:59,150 --> 00:15:02,500 and we'll be doing that actually in the next video. 324 00:15:02,500 --> 00:15:03,960 I used the print function here 325 00:15:03,960 --> 00:15:05,720 because it's a visual function, 326 00:15:05,720 --> 00:15:07,620 so it's easier to see what's going on. 327 00:15:07,620 --> 00:15:09,920 The aim was to show you how to use and manipulate 328 00:15:09,920 --> 00:15:12,490 the kwargs dictionary and how it's important 329 00:15:12,490 --> 00:15:16,320 to retain the expected behaviour of the original function. 330 00:15:16,320 --> 00:15:17,980 Now I've said a few times that if the aim 331 00:15:17,980 --> 00:15:20,550 was to create a version of print that prints backwards, 332 00:15:20,550 --> 00:15:22,220 then I wouldn't be doing it this way. 333 00:15:22,220 --> 00:15:24,150 I'm gonna finish the video by showing you 334 00:15:24,150 --> 00:15:27,150 the code I would write if the aim had been 335 00:15:27,150 --> 00:15:28,640 just to print backwards. 336 00:15:28,640 --> 00:15:30,090 Let me go ahead now and add that 337 00:15:30,090 --> 00:15:33,170 just to show you how that would work. 338 00:15:34,900 --> 00:15:39,070 And it would be def backwards_print *args comma and **kwargs 339 00:15:44,000 --> 00:15:46,920 sep_character equals kwargs.pop sep 340 00:15:53,750 --> 00:15:55,750 and then the space in single quotes, 341 00:15:55,750 --> 00:15:59,420 then we'll do print, sep_character.join word 342 00:16:06,970 --> 00:16:10,720 and in square brackets, ::-1 for word in args 343 00:16:13,990 --> 00:16:16,830 and then left square bracket, ::-1 344 00:16:16,830 --> 00:16:20,750 then a right square bracket, a right parenthesis, 345 00:16:20,750 --> 00:16:24,910 comma, **kwargs and then a final right parenthesis. 346 00:16:27,910 --> 00:16:29,880 Now backwards_print, as you can see here, 347 00:16:29,880 --> 00:16:32,750 joins the reversed words using the join method. 348 00:16:32,750 --> 00:16:34,720 So this would be the way that I would normally do it 349 00:16:34,720 --> 00:16:37,220 and it actually uses something called a list comprehension 350 00:16:37,220 --> 00:16:39,120 which we haven't looked at yet 351 00:16:39,120 --> 00:16:41,240 but we'll be looking at those later in the course. 352 00:16:41,240 --> 00:16:43,790 So again, if the aim was to create a version of print 353 00:16:43,790 --> 00:16:45,500 that prints backwards, I wouldn't have done it 354 00:16:45,500 --> 00:16:47,440 the way that I've shown you earlier in the video. 355 00:16:47,440 --> 00:16:49,400 We've done it that way just to really explore 356 00:16:49,400 --> 00:16:52,390 what kwargs is and args and how to use them. 357 00:16:52,390 --> 00:16:54,240 Anyway, I'll leave it there 358 00:16:54,240 --> 00:16:57,240 and we'll see you in the next video.