1 00:00:05,280 --> 00:00:06,750 Welcome back everyone to functions. 2 00:00:06,750 --> 00:00:12,370 Part two in part two we're really going to focus on trying to solve problems with functions and also 3 00:00:12,390 --> 00:00:18,540 cover a few useful operators such as the joint method off of the string as well as things like max and 4 00:00:18,540 --> 00:00:18,980 min. 5 00:00:19,170 --> 00:00:20,370 Let's get started. 6 00:00:20,370 --> 00:00:24,120 All right let's start off by actually going through a few useful operators or functions that we haven't 7 00:00:24,120 --> 00:00:25,070 discussed before. 8 00:00:25,200 --> 00:00:31,470 Such as Max maximun enumerate and the join method off of the string We'll start off with maximun since 9 00:00:31,470 --> 00:00:32,840 they're kind of the easiest. 10 00:00:32,850 --> 00:00:36,640 These are actually just going to return the max Borman of what you passen. 11 00:00:37,010 --> 00:00:40,320 So it's only pasand to numbers into max and min. 12 00:00:40,440 --> 00:00:42,820 Such as a tour of three. 13 00:00:43,070 --> 00:00:44,060 And then I print this out. 14 00:00:44,060 --> 00:00:46,950 So what's the max between 2 and 3. 15 00:00:47,040 --> 00:00:50,930 If I save that and run this I get back 3. 16 00:00:50,930 --> 00:00:54,550 So if you just pasand two numbers like this I'll report back. 17 00:00:54,680 --> 00:00:59,120 Which is the max number where you can also do for a large amount of numbers. 18 00:00:59,240 --> 00:01:03,090 It's just passing the string of values or excuse me a list of values. 19 00:01:03,110 --> 00:01:08,320 So here I am passing in a bunch of values inside of a list and then when you pass that list instead 20 00:01:08,320 --> 00:01:11,330 of Max over turn back the largest value in that list. 21 00:01:11,330 --> 00:01:13,020 So in this case it was 100. 22 00:01:13,100 --> 00:01:18,140 And just like Max there's also a min function which as you may have guessed returns back the minimum 23 00:01:18,140 --> 00:01:21,670 value in that list for the minimum between two numbers. 24 00:01:21,680 --> 00:01:24,900 Second pasan for instance 1 in 100. 25 00:01:25,070 --> 00:01:27,660 Save that and then get back 1. 26 00:01:27,920 --> 00:01:30,580 So that's max and min. 27 00:01:30,680 --> 00:01:34,910 Up next I want to talk about the enumerate function which is actually really useful especially when 28 00:01:34,910 --> 00:01:37,290 used with for loops. 29 00:01:37,340 --> 00:01:38,020 So let's imagine. 30 00:01:38,060 --> 00:01:40,450 I want to do a for loop through a list of letters. 31 00:01:40,520 --> 00:01:52,460 So I say four letter in a b and c and then I said Prince Lutter and I'm going to delete this max and 32 00:01:52,460 --> 00:01:53,950 min appear. 33 00:01:53,950 --> 00:01:59,480 So when I run this I should see ABC as illustrate a b and c.. 34 00:01:59,860 --> 00:02:07,810 So in fact we can say copy that set my list equal to that list and then just say four letter in my list 35 00:02:09,320 --> 00:02:12,050 run the second and we'll get back the same result. 36 00:02:12,050 --> 00:02:12,720 Now let's imagine. 37 00:02:12,740 --> 00:02:16,810 I also want to know the index location of each of these letters. 38 00:02:16,820 --> 00:02:21,680 Well one way I could do this is start by having an index parameter. 39 00:02:21,950 --> 00:02:24,170 So something like Index is equal to zero. 40 00:02:24,470 --> 00:02:26,390 And it's a four letter in my list. 41 00:02:26,390 --> 00:02:35,580 Print the letter and then print is at index and then maybe I can use that formatting here. 42 00:02:36,910 --> 00:02:38,660 The format index. 43 00:02:38,690 --> 00:02:44,420 And then I'll add one to the index and they'll say indexes equal to index plus 1. 44 00:02:44,420 --> 00:02:49,460 So what I'm doing here is I set this variable index to 0 and then I'm going to say OK for every letter 45 00:02:49,460 --> 00:02:54,520 in my list a b and c I'll print out the letter and then I'll say is that index. 46 00:02:54,650 --> 00:02:59,940 And then I'll print out the index there not add one to my index and then I'll just print a blank line. 47 00:03:02,370 --> 00:03:04,220 So let's say that and see what happens. 48 00:03:05,450 --> 00:03:07,560 And I going expand this so you can see. 49 00:03:07,900 --> 00:03:10,250 So it says A is an index 0. 50 00:03:10,450 --> 00:03:13,760 B is the index 1 and C is an index to. 51 00:03:13,790 --> 00:03:20,470 OK not bad but this is such a useful task or such a common task as far as keeping track of the index 52 00:03:20,530 --> 00:03:26,020 while you're iterating that Python already has a built in function to do this and it's called enumerate 53 00:03:26,080 --> 00:03:29,410 because it can enumerate this list. 54 00:03:29,410 --> 00:03:35,310 So what you do is instead of having that manually track the index as we just did you just passed in 55 00:03:36,850 --> 00:03:37,670 your iterable. 56 00:03:37,690 --> 00:03:41,620 In this case our list into this enumerate function. 57 00:03:41,620 --> 00:03:44,320 And so let's see what enumerate actually returns. 58 00:03:44,500 --> 00:03:52,730 On the say for item in the numerator my list prints out the item. 59 00:03:52,750 --> 00:03:58,600 So when I run this you'll notice that you get back these tuple pairs where you have the first item in 60 00:03:58,600 --> 00:04:04,820 the tuple be the index position and the second item be the actual element that's inside of that list. 61 00:04:04,900 --> 00:04:10,190 Essentially something we're doing really similar before except now it's automatically done for you enumerate. 62 00:04:10,270 --> 00:04:18,300 Now we can continue this by actually using tuple and packing so I can say for index Khama item and enumerate. 63 00:04:18,460 --> 00:04:23,950 And now I'm going to unpack these tuples as we discussed in the for loop lecture to actually grab their 64 00:04:23,950 --> 00:04:26,080 index positions and I can say prints. 65 00:04:26,110 --> 00:04:36,610 Item print is an index and in fact then I can use extreme formatting here since I'm on Paice on 3.6 66 00:04:38,690 --> 00:04:45,580 and let's print out them of Lynn Klein save it run this and I get back the same result as I did for 67 00:04:46,260 --> 00:04:48,230 the index 0 Baeza index 1. 68 00:04:48,240 --> 00:04:54,090 See is the index to except that takes a lot less code now because the numerate function I could automatically 69 00:04:54,090 --> 00:04:58,440 grab that index because it's numbering every item in that list. 70 00:04:58,440 --> 00:05:00,340 So that's how the enumerate function works. 71 00:05:00,360 --> 00:05:05,970 And it's super useful when you want to keep track of items or maybe switch something out at a particular 72 00:05:05,990 --> 00:05:06,990 index location. 73 00:05:06,990 --> 00:05:10,830 So if you want to switch out every even number something you could do that as well. 74 00:05:12,520 --> 00:05:19,290 OK now I'm going to cover one last useful operator which is the dot join method off a string. 75 00:05:19,360 --> 00:05:28,330 So let's imagine I have a list of letters again a B and C and I wanted to somehow join the list into 76 00:05:28,330 --> 00:05:29,210 a single string. 77 00:05:29,380 --> 00:05:33,410 I wanted my output to look something like just ABC a single string like that. 78 00:05:33,670 --> 00:05:36,580 Or if I had the end here I'd also want the D in there 79 00:05:39,490 --> 00:05:41,840 so I'd want to look something like that. 80 00:05:41,890 --> 00:05:44,340 So how can I actually do that when I have this list. 81 00:05:44,530 --> 00:05:47,990 Well luckily there's a method you can call off a string. 82 00:05:48,030 --> 00:05:49,390 So let me show you how that works. 83 00:05:50,390 --> 00:05:56,280 You call part of a string that you want to serve as a connector between each of these elements. 84 00:05:56,450 --> 00:06:00,890 Then you say join and then you just pass in the list. 85 00:06:00,890 --> 00:06:08,290 So let's print out this result so we can see what it looks like and when say print. 86 00:06:08,490 --> 00:06:13,130 And I'm going to save that lots from this and then as I get back. 87 00:06:13,200 --> 00:06:14,550 ABC. 88 00:06:14,810 --> 00:06:19,700 So what this is actually doing is you get to choose whatever stream connector you want in between these 89 00:06:19,700 --> 00:06:21,850 elements and then you join them together. 90 00:06:22,100 --> 00:06:26,080 For example I'll choose two sets of dashes as my string. 91 00:06:26,210 --> 00:06:28,980 Then I called Dot join and I pass in my list. 92 00:06:29,120 --> 00:06:30,960 I print out the result to that. 93 00:06:31,360 --> 00:06:37,890 Then I get to see every element in that list 2 dashes then the next element to ashes then the next element. 94 00:06:37,940 --> 00:06:45,450 So to make it really clear what's happening here I and to say dash X dash run this again and I can see 95 00:06:45,630 --> 00:06:50,550 every element in the list separated are joined together by Dash X dash. 96 00:06:50,580 --> 00:06:52,160 Again you choose the connector. 97 00:06:52,160 --> 00:06:54,350 They say that join and pass and the list. 98 00:06:54,620 --> 00:06:54,900 OK. 99 00:06:54,930 --> 00:06:58,480 So those are the three useful operators I wanted to discuss. 100 00:06:58,480 --> 00:07:02,430 Now let's practice two example problems of Python functions. 101 00:07:02,430 --> 00:07:06,930 All right the first problem is to write a function that returns a boolean in the of the word secret 102 00:07:07,050 --> 00:07:08,240 isn't a string. 103 00:07:08,240 --> 00:07:09,170 So let's try that. 104 00:07:10,340 --> 00:07:15,820 Well start off base in the keyword DPF and then we'll name our function we'll call it secret underscore 105 00:07:15,820 --> 00:07:19,690 check and then we need to accept the string as an argument. 106 00:07:20,670 --> 00:07:23,630 So see my string colon. 107 00:07:24,020 --> 00:07:28,170 And I want you to perform some sort of logic to check if the secret is in the string. 108 00:07:29,320 --> 00:07:31,960 So I'll say if secret. 109 00:07:32,530 --> 00:07:34,300 Let's make sure I spell this right. 110 00:07:34,300 --> 00:07:42,060 Secrets in my string return true. 111 00:07:43,780 --> 00:07:49,590 Else return false and in just a little bit I'll show you how you can improve upon this. 112 00:07:49,590 --> 00:07:51,960 But right now let's see what this logic is doing. 113 00:07:52,000 --> 00:07:57,040 We taken a string as an argument and I check is this string secret in my string. 114 00:07:57,040 --> 00:08:00,550 If so all return TRUE else return false. 115 00:08:00,860 --> 00:08:03,730 So test it out and make sure it's actually working. 116 00:08:03,730 --> 00:08:09,210 Mizu much the little bit so you can see everything and then I'm going to print the results of secret 117 00:08:09,220 --> 00:08:13,430 check and Wil's passen the string simple. 118 00:08:13,540 --> 00:08:16,120 So here I would expect it to return false. 119 00:08:16,540 --> 00:08:18,580 So I run this and I get back false. 120 00:08:18,580 --> 00:08:20,370 Now let's try something like. 121 00:08:20,470 --> 00:08:27,060 This is a secret and that when I run this I get back. 122 00:08:27,060 --> 00:08:29,880 True because secret is within that string. 123 00:08:29,920 --> 00:08:33,190 OK so something I want to point out is. 124 00:08:33,340 --> 00:08:36,120 Let's analyze what secret in my string is. 125 00:08:36,130 --> 00:08:38,050 This is already a boolean. 126 00:08:38,050 --> 00:08:39,440 So we're basically saying. 127 00:08:39,490 --> 00:08:42,630 If true return TRUE else return false. 128 00:08:42,730 --> 00:08:46,670 In that case I might as well just return the result of this comparison. 129 00:08:46,710 --> 00:08:53,450 Or this operation secret in my string so I can actually place this whole thing but just saying Return 130 00:08:54,380 --> 00:08:58,720 secret in my stream because that is what's happening here. 131 00:08:58,730 --> 00:09:00,060 This itself is the boolean. 132 00:09:00,080 --> 00:09:04,880 So there's no need for me to add more returns of booleans and said I'll just return this directly. 133 00:09:04,880 --> 00:09:06,110 True or false. 134 00:09:06,170 --> 00:09:09,020 So if I run this I'll get back the same results. 135 00:09:09,020 --> 00:09:15,930 True for this the last thing I want to know is let's imagine we have an edge case where we have an s 136 00:09:15,960 --> 00:09:16,640 capitalized. 137 00:09:16,660 --> 00:09:23,760 Here when I run this I now get back false because my check is only performing it for the lower case 138 00:09:23,820 --> 00:09:24,900 secret. 139 00:09:24,960 --> 00:09:30,670 I could add logical operators like and and or statements to check for various cases of secret. 140 00:09:30,930 --> 00:09:36,540 But instead what I could do is I could just lower case everything in the string first by calling the 141 00:09:36,780 --> 00:09:38,600 lower method off that string. 142 00:09:38,730 --> 00:09:44,750 Then I'll check if secret is in the lower case version of that string then return true or false. 143 00:09:44,760 --> 00:09:47,310 So now let's see what happens. 144 00:09:47,320 --> 00:09:48,300 Now I get back. 145 00:09:48,340 --> 00:09:53,350 True because secret when I lower case this is in that string. 146 00:09:53,370 --> 00:09:53,620 All right. 147 00:09:53,630 --> 00:09:57,200 So that's how we can work through a word problems such as this. 148 00:09:57,200 --> 00:09:57,410 Right. 149 00:09:57,410 --> 00:10:02,700 The function returns a boolean true or false indicating that word secret is in string OK. 150 00:10:02,700 --> 00:10:05,630 Problem 2 is to create a code maker function. 151 00:10:05,640 --> 00:10:10,770 This function will take in a string name and replace any vowels with the letter x. 152 00:10:10,770 --> 00:10:14,060 So let's break this down into a function that can hopefully solve this problem. 153 00:10:15,130 --> 00:10:21,150 Well call this function codebreaker and it will accept that string. 154 00:10:21,190 --> 00:10:24,120 So let's see how we can do this. 155 00:10:24,190 --> 00:10:29,710 First I'm going to want to have some sort of way to organize my output and then what I should be doing 156 00:10:29,800 --> 00:10:33,010 is iterating through every letter in the string. 157 00:10:33,310 --> 00:10:35,850 So start by iterating through every letter in the string. 158 00:10:35,860 --> 00:10:42,150 So I'll say four letter in my string. 159 00:10:42,290 --> 00:10:45,810 In this case let's just print out the letters to see if that works. 160 00:10:47,200 --> 00:10:52,900 And let's have coachmaker run on a line will say coachmaker and will say Samie 161 00:10:55,640 --> 00:10:57,660 only run this I get back. 162 00:10:57,830 --> 00:10:59,990 S a m m y. 163 00:11:00,140 --> 00:11:00,680 And that true. 164 00:11:00,680 --> 00:11:02,430 Looks like I still have this code above here. 165 00:11:02,510 --> 00:11:04,620 No comment that out. 166 00:11:04,800 --> 00:11:06,570 OK so we have this code make her function. 167 00:11:06,810 --> 00:11:10,620 We just saw how we could iterate through every letter in that string. 168 00:11:10,620 --> 00:11:14,380 Now I want to check if those letters are vowels. 169 00:11:14,520 --> 00:11:15,850 So how can I do that. 170 00:11:15,960 --> 00:11:25,060 While I can do this with another for loop I could then say for vowel N and then it could have a string 171 00:11:25,060 --> 00:11:26,690 of values here a. 172 00:11:26,820 --> 00:11:40,160 Oh you and in this case I'm gonna say Prince letter equals equals vowel and let's go ahead and print 173 00:11:40,160 --> 00:11:44,680 out the letter itself that tab out there OK. 174 00:11:44,690 --> 00:11:49,730 So my logic here right now I'm just slowly building out the capabilities I take in that string for every 175 00:11:49,730 --> 00:11:56,370 letter in that string on my check against every vowel and I owe you or a IOU and then print it out if 176 00:11:56,370 --> 00:11:57,390 there is a match. 177 00:11:57,440 --> 00:11:58,420 So let's run this again. 178 00:11:59,500 --> 00:12:04,100 So you'll notice here in our results it's going to be printing a bunch of falses because it's checking 179 00:12:04,460 --> 00:12:06,880 each letter about five times. 180 00:12:06,890 --> 00:12:11,630 So how about little change just print statements only print out if there is actually a match. 181 00:12:11,720 --> 00:12:19,810 Some of the following I'll say if the letter is equal to the vowel then print out the letter that way 182 00:12:19,880 --> 00:12:21,630 only see the vowels being printed out. 183 00:12:21,800 --> 00:12:23,350 So let's run this again. 184 00:12:23,750 --> 00:12:28,510 And now I get back the letter A perfect because I was the only vowel in Samie. 185 00:12:28,970 --> 00:12:30,420 So now we're actually getting somewhere. 186 00:12:30,440 --> 00:12:35,800 I now have the capability to go through every letter in the string check it against every possible vowel 187 00:12:36,020 --> 00:12:39,320 and if the letter is equal to that I'll do something. 188 00:12:39,320 --> 00:12:42,220 Now the idea is just the actual replacement. 189 00:12:42,470 --> 00:12:44,790 So there's various ways we could do the replacement. 190 00:12:44,900 --> 00:12:54,380 But one interesting way would be right before we do the for loop we create a list from my string and 191 00:12:54,390 --> 00:12:57,750 just want to print what that actually looks like for you. 192 00:12:57,980 --> 00:13:00,010 So I'll print out that output. 193 00:13:00,110 --> 00:13:06,290 So now I have a list out of the characters Sammy and then I'm going to say for every letter in my string 194 00:13:07,220 --> 00:13:13,490 check those letters are vowels and if the letters equal to value vowel I should replace that output 195 00:13:13,490 --> 00:13:14,320 position. 196 00:13:14,690 --> 00:13:16,640 So that's where I'm going to use enumerate. 197 00:13:17,030 --> 00:13:21,620 We'll say for index letter in enumerate my string 198 00:13:24,250 --> 00:13:30,610 check that letter or basically for every vowel then you check that the letter is equal to that vowel 199 00:13:30,700 --> 00:13:39,100 and if that happens to be the case I'm going to take the output list at that index position and set 200 00:13:39,100 --> 00:13:42,340 it equal to x as the instructions wanted me to. 201 00:13:42,340 --> 00:13:47,230 So you got to remember we want to take the string and replace any vowels with the letter x. 202 00:13:47,290 --> 00:13:53,680 So right now I have this output which is this list then I'm going to say OK for every single index and 203 00:13:53,680 --> 00:13:57,590 letter and enumerate my street check it against the vowel. 204 00:13:57,700 --> 00:14:01,720 If we have a match grab my output at that sugar index positions. 205 00:14:01,720 --> 00:14:06,790 The first is going to be on the A and replace it with an X and then at the end of all this. 206 00:14:06,910 --> 00:14:14,450 Let's see what happens when we return our output and pay very close attention to my indentation here 207 00:14:14,480 --> 00:14:16,430 and zoom out so you can see the whole picture. 208 00:14:16,430 --> 00:14:21,490 So again I'm returning output after going through these four loops. 209 00:14:21,540 --> 00:14:23,450 So again take note of that in the notation. 210 00:14:23,460 --> 00:14:26,280 You can always copy and paste from are provided notes. 211 00:14:26,310 --> 00:14:29,630 So let me say that and see what happens when I run this. 212 00:14:29,830 --> 00:14:31,870 Right now I'm still not replacing a. 213 00:14:31,900 --> 00:14:34,250 So let's try to debug. 214 00:14:34,270 --> 00:14:36,380 So what's happening here is I'm just printing the output. 215 00:14:36,400 --> 00:14:41,740 So let's delete this print function and then since I'm returning the output I'm not going to need to 216 00:14:41,770 --> 00:14:48,440 print the results of coachmaker and that should fix that issue. 217 00:14:48,480 --> 00:14:51,190 So the Samie that was coming from that print output. 218 00:14:51,240 --> 00:14:52,530 So now we're returning the output. 219 00:14:52,530 --> 00:14:56,380 After doing these changes and then printing out the result of code maker. 220 00:14:56,550 --> 00:14:57,960 So let's run this again. 221 00:14:57,960 --> 00:15:00,880 And now I see s x and y. 222 00:15:00,900 --> 00:15:01,800 Perfect. 223 00:15:01,800 --> 00:15:06,210 Now the last thing you need to do is fix the output Scotius the string and we really talked about how 224 00:15:06,210 --> 00:15:09,890 it could do that using the join method. 225 00:15:09,910 --> 00:15:19,540 So once that's done I can just say output is equal to an empty string and then join the output. 226 00:15:19,560 --> 00:15:23,820 And now when I run this I'll get back the actual string itself. 227 00:15:23,820 --> 00:15:26,950 Now keep in mind we're only checking for lowercase vowels. 228 00:15:26,970 --> 00:15:35,370 So something we do here is say If letter that lowercase is equal to these lowercase vowels then the 229 00:15:35,370 --> 00:15:36,500 replacement as well. 230 00:15:36,690 --> 00:15:42,290 So that would fix an issue something like Adam which starts of a capital A. 231 00:15:43,190 --> 00:15:43,820 So we run this. 232 00:15:43,820 --> 00:15:45,820 Now I see X the XM. 233 00:15:46,220 --> 00:15:48,690 OK so let's quickly go over this logic again. 234 00:15:48,710 --> 00:15:53,520 Because the probably the most complex example of Python code I've seen so far. 235 00:15:53,600 --> 00:15:57,960 Basically what I'm doing here is I create this output list. 236 00:15:58,260 --> 00:16:05,170 Then for every index and letter inside of my original string I check it against every possible vowel. 237 00:16:05,450 --> 00:16:10,940 And then I say hey if that letter lowercase is equal to one of those vowels go ahead and change the 238 00:16:10,940 --> 00:16:15,860 output index position at that list to the letter X. Then to get it back to a string. 239 00:16:15,860 --> 00:16:19,260 I'm simply going to join the outputs and return the output. 240 00:16:19,620 --> 00:16:20,160 OK. 241 00:16:20,300 --> 00:16:23,080 If you have any questions feel free to post the Kewney forums. 242 00:16:23,090 --> 00:16:26,960 This is definitely probably the most advanced jump we've made so far but we're going to get a lot more 243 00:16:26,960 --> 00:16:31,310 practice in the very next lecture through a bunch of function exercises. 244 00:16:31,310 --> 00:16:32,020 We'll see you there.