Now let's talk about string slicing.
In case you missed it, here are the previous parts of the series
0:00 There my beautiful children,
0:01 in this video we're gonna talk about string slicing.
0:04 What is string slicing?
0:06 We're not talking about cake slicing, so let's get started.
0:09 Well a string as you remember
0:11 was that thing in the green here,
0:13 but that's just really specific
0:15 to the IDE that we're using,
0:17 if you're using any other text editor it's not necessarily
0:19 gonna be green.
0:20 So the string is just something in quotes.
0:22 Either it's single quotes or double quotes
0:24 as long as it's consistent,
0:27 Can't have a single quote ending with a double quote.
0:30 They gotta match.
0:34 So we have to match with the quotes,
0:37 that's your string, right.
0:39 So what we want to do now is slice those strings.
0:43 Well, what does that mean?
0:46 Imagine I gave you an email address.
0:48 Email is equal to, I don't know,
0:52 rafeh at gmail dot com,
0:56 something like that.
0:57 Well, a common thing that people have to do when they
1:00 are getting this data back is,
1:03 well, this is the username or something,
1:08 this part is the Gmail thing,
1:13 and then this is the dot com part, right.
1:16 So like, let's say we just want the domain or whatever,
1:19 and here we simply want like the username.
1:22 So how would we do that?
1:24 Well, we can use a little bit of string slicing.
1:27 So let's just start with a simple example.
1:29 Let's take hello, and let's say we want to get the first
1:32 Let's take hello, and let's say we want to get the first
1:35 letter from hello, we wanna get just the H.
1:38 Well, how you do it is you index by opening a bracket,
1:42 and closing a square bracket.
1:44 And if I do zero, it'll get me
1:48 the first letter of that, okay.
1:51 So H in this case is zero, right.
1:53 So H in this case is zero, right.
1:55 The E is one, in Python most of the things start from zero.
1:59 So we go all the way up to this O here,
2:02 which is a four, okay.
2:07 So we take this hello and
2:13 let's take this hello and let's simply do a 1,
2:16 let's take this hello and let's simply do a 1,
2:19 and that'll give me the E, okay.
2:21 Now another thing I want to show you guys in string slicing,
2:24 besides doing, okay that index,
2:27 right, this passing in the index one,
2:31 will give me the second letter.
2:32 What if we want to do something cooler
2:33 like get a chunk of code?
2:36 Well, how indexing works is it's start, colon stop.
2:39 Well, how indexing works is it's start, colon stop.
2:43 Okay, colon stop.
2:46 So what you can do is you can say hello.
2:49 Oh, I keep doing that.
2:51 Hello, and you can say start from zero, and end at two.
2:54 Hello, and you can say start from zero, and end at two.
2:57 Not including two, but end at two.
3:01 So include zero, but don't include the two.
3:04 Which means that you really get the zeroth str um
3:07 zeroth index
3:09 and the first index.
3:11 Right, so whatever the letter is at the zeroth index,
3:13 and whatever the letter is at the first index.
3:16 So in this case we'll get an H E, okay.
3:21 How you can read this is just,
3:22 give me the first two letters, that's how I read it.
3:25 So you can just say give me the first two letters.
3:28 Now when you're starting off from zero,
3:30 by default index starts at zero.
3:33 So if you don't actually say this at all,
3:35 and you just remove the zero,
3:36 you're gonna get back H E, okay.
3:41 Everything that I'm showing you guys here,
3:44 play around with it, okay?
3:45 Don't just sit here and watch my videos.
3:48 I don't want you to be a passive learner,
3:49 please, please actively do this with me.
3:52 please, please actively do this with me.
3:55 Or pause my video and do this.
3:56 I want you to spend more time doing
3:58 and less time looking at it, okay.
4:00 Because it seems really simple when you're watching it,
4:03 but if you don't put it into action and do things
4:05 that make sense to you,
4:07 if you don't turn it into a game for yourself where you're
4:10 doing something, you know like
4:11 you making fun little stupid projects,
4:14 using what I'm showing you,
4:17 you're not gonna be able to remember it.
4:19 That's really what my problem with Codecademy is,
4:22 a lot of people go through Codecademy,
4:24 but the problem that ends up happening is that
4:27 they just go through it at a really fast pace
4:30 and they don't really have much
4:31 projects that they get to do there,
4:33 and not a lot of stuff that they get to do on their own,
4:36 so the most common complaint you hear from people
4:39 who take the Codecademy course will be like,
4:41 "It was great, I took the whole thing!"
4:42 But, yeah, right now, I can't write a single line of code,
4:46 okay, so it's not impressive the higher
4:49 you are in really abstract levels
4:51 introduction to classes,
4:52 "Oh yeah, I know all about function,
4:54 I'm in introduction to classes."
4:55 Write a function.
4:57 Write a function that takes in three inputs
4:58 and does dadada, print something out and sort in order.
5:02 "Pfft, I don't know how to do that, I'm totally lost."
5:06 Don't be one of those people,
5:07 make sure you build strong fundamentals,
5:09 and your coding level is functional at all times, right.
5:13 So even if I'm teaching you really basic stuff,
5:15 make sure you can do something with it.
5:17 That's the only way you'll get better
5:19 and make sure you have fun while doing it.
5:21 Anyway, let's get back to it.
5:22 So, hello, right.
5:26 Make up your own strings and break them up
5:28 and see what you can make up from what I have shown you here
5:31 and experiment, what if I change the end,
5:35 what if I change the stop part of it,
5:37 and what if I change the start part of it,
5:39 what if I don't put anything in the stop part, what happens?
5:41 So let's try that.
5:42 So hello and let's put in nothing, for both parts,
5:46 So hello and let's put in nothing, for both parts,
5:48 let's see what happens.
5:49 You just get the whole string, by default,
5:52 it starts from zero and by default
5:53 it ends at the last index.
5:57 Okay, so, it's the same thing as saying zero
6:01 to if you count it up, zero, one, two, three, four, right?
6:05 to if you count it up, zero, one, two, three, four, right?
6:06 O is four, so I'll say four here, that will not give me it
6:07 O is four, so I'll say four here, that will not give me it
6:10 I have to say five.
6:13 Right, because it will not include the four,
6:16 if I say four in will go up to but won't include the four.
6:19 For example,
6:22 So we have to do five, okay?
6:26 So that helps us get to the end of the string.
6:30 Now what if I wanna get the last letter from hello?
6:33 Or anything, if I wanna get the last letter,
6:36 I can do something like this.
6:41 Okay, I can also slice by a negative number.
6:45 So if I wanna get hell from hello,
6:47 I can do hello and I can say go from zero
6:50 I can do hello and I can say go from zero
6:55 and let's try see what happens if I put negative one here.
7:01 So another way I.
7:02 Basically, what I'm saying is,
7:04 start from the zeroth part go up to
7:09 the last part but not including the last part,
7:12 so that gave me hell.
7:14 Another way to write it is by putting a four here, okay.
7:17 Another way to write it is by putting a four here, okay.
7:21 Another way to write it is not having a zero here.
7:23 Another way to write this is not having a zero here.
7:26 That all gives you hell.
7:27 So you see, play around with all those.
7:29 I'm gonna now show you another thing
7:32 that you can slice with and that'll also blow your mind.
7:36 Slicing is very important, it's a very common procedure,
7:40 so it's pretty go to learn it because,
7:42 let's say you are trying to make an app
7:45 which goes on craigslist and pulls
7:47 a lot of data from craigslist,
7:49 so like pull up ads, so that ads, like
7:51 you might get the data back in a string form.
7:54 So you might get something like,
7:56 XBOX 360 pricing is,
8:02 it's price is $10 and
8:05 that's stupid, it's not $10, right,
8:07 you might get it for $150 nowadays,
8:11 2016 the value of it has significantly dropped,
8:15 and then let's say it says the condition type,
8:18 so the condition type is new, right.
8:22 So this is the
8:26 data that you'd get from craigslist.
8:28 Well, if you were writing up script or python code
8:31 Well, if you were writing up script or python code
8:34 that would pull that information
8:36 and then make sense out of it for you
8:39 and like write it to an actual excel file,
8:42 so like you want it to, you know, essentially do something
8:46 cool where it opens up a excel and writes to it
8:50 and you want it to like have,
8:53 you know, product,
8:58 and condition, right,
9:00 and in product you'd want XBOX 360,
9:04 in price you'd want 150
9:07 and in condition you'd want new, right.
9:11 How would pull that data cleanly
9:13 so it doesn't put XBOX 360, 150, new all in one place?
9:17 so it doesn't put XBOX 360, 150, new all in one place?
9:21 So for that you need to be able to do string slicing, okay.
9:25 So for that you need to be able to do string slicing, okay.
9:28 So for instance, you might say,
9:31 console or product, right, or console product
9:35 is equal to, you know, find me the first pipe, right.
9:39 is equal to, you know, find me the first pipe, right.
9:42 So like let's say we have this guy here, there is a method
9:45 So like let's say we have this guy here, there is a method
9:48 you can do on data which is called index.
9:51 you can do on data which is called index.
9:54 So let's find the index of pipe.
10:00 It tells me that pipe is at index nine,
10:02 so zero, one, two, three, four,
10:06 five, six, seven, eight, nine.
10:10 Which means that if I index the string data
10:15 and I do nine, It'll give me back the pipe.
10:19 So what that tells me is that to get XBOX 360,
10:22 I need to go from the start of that string,
10:26 all the way up to the first pipe,
10:28 that should get me the product.
10:30 So I can say product is equal to data
10:33 from the start I don't need to say zero, right?
10:36 I can say from the start to
10:41 take the data dot index of the pipe.
10:48 Now if I show you product, boom.
10:51 Look at that, we got XBOX 360.
10:54 And so now I can write that product to the file,
10:57 teach you guys how to read and write to files.
10:59 Okay so then what tt will do is that it'll actually write
11:02 XBOX 360 in here for you, automagically.
11:06 Now, understand the power and implications,
11:09 "Well, why can't I just do that by hand?" Right?
11:11 That might be a question.
11:12 What if it was a hundred thousand products?
11:14 Can't do it by hand, good luck, right?
11:17 What if a million products that you were trying
11:19 to search from and find the best price
11:21 using your craigslist bot.
11:24 That's where programming comes in, okay?
11:26 It's very important to understand how programming in here
11:29 ties together and how it's more powerful
11:32 than you trying to do this on your own.
11:35 So that's really the power of string slicing, okay?
11:39 To break this line down for you a little bit more,
11:42 data, colon, that's just saying start from zero,
11:46 and then I'm saying data dot index of pipe,
11:49 what does that part evaluate to, right?
11:51 Dot index is a method that you can use on data, that's, okay
11:55 Dot index is a method that you can use on data, that's, okay
11:57 which just gives you something that's you're looking for,
12:00 you pass it into the function, right, that function
12:02 or that method index takes in one argument.
12:06 So what does this whole part evaluate to in our case?
12:09 This part evaluates to a nine.
12:12 Right, this whole part data do index, right?
12:16 Evaluates to nine, so if I do data zero through nine,
12:20 you can see that I just get XBOX 360, the same way.
12:23 Nine tells me up to but not including the pipe, okay.
12:26 Nine tells me up to but not including the pipe, okay.
12:29 So that's how we got the XBOX 360 part,
12:33 how would you get the 150?
12:35 You would kind of do the same way to get the price, okay.
12:39 You would kind of do the same way to get the price, okay.
12:40 But you would say instead of starting to look from here,
12:45 because then it'll find this pipe right here,
12:47 right, this one.
12:48 You wanna find this pipe now.
12:51 So you want to actually start your string search
12:55 from this location or this location that I'm highlighting.
12:59 And then you wanna search all the way up to this pipe
13:03 and stop there and get whatever
13:06 is in between these two pipes, okay?
13:09 So that's something I want you guys to try,
13:12 paste your code below for how you might get
13:15 the price and the condition, okay.
13:18 That would be a fun thing for you guys to do.
13:22 I'm gonna keep moving on
13:23 and talk a little bit more about string,
13:26 string slicing, cause there is still
13:28 a little bit more to it.
13:32 and again I want to keep practicing all this,
13:34 cause otherwise this is gonna overwhelm you,
13:37 all this knowledge.
13:40 So let's say that I have
13:44 I can do start, stop and here is another method
13:46 I can do start, stop and here is another method
13:48 to blow your mind, step.
13:50 So how many steps do wanna take when I'm reading something.
13:55 So like let's say, I have this string,
13:59 "Hi how are you doing, it is very nice to meet you."
14:02 "Hi how are you doing, it is very nice to meet you."
14:07 I wanna make sure I'm consistent so not
14:10 double quote single quote and um
14:14 you know, let's just store that in some variable greeting.
14:18 So if I say greeting so you can see the whole string,
14:22 so what I can do is take greeting, say start at zero,
14:28 stop at, I don't know, negative one,
14:31 so like all the way at the end,
14:33 and then I want you to.
14:37 Basically it'll go up to O, right?
14:40 Because it's up to like,
14:41 or sorry, it'll go up to the U part
14:44 but not this period right here.
14:48 I just, it won't let me highlight that period.
14:52 It won't go up to that period, okay.
14:54 It'll go up to U, because it's up to
14:56 but not including the period.
14:58 Sorry, I keep saying that a lot but I do know that
15:01 when you're starting to learn python or programming,
15:04 those things you'll forget a lot.
15:06 So I'm sorry if I'm reiterating
15:07 that fact over and over again.
15:09 Alright so we start from zero, we go up to the u, right?
15:11 Alright so we start from zero, we go up to the u, right?
15:14 We go from here all the way to here,
15:17 and then we wanna step, so instead of a,
15:23 for example, taking, I don't know,
15:26 reading every single one of these,
15:28 we can read every other letter.
15:30 So I can say instead of stepping by one which is default,
15:33 if I do one here you'll see,
15:36 this is pretty much the same string without the period.
15:39 And if I do nothing here, you'll see the same thing, right,
15:42 And if I do nothing here, you'll see the same thing, right,
15:44 cause that's a default.
15:46 And if I do step by two, this is basically saying
15:47 And if I do step by two, this is basically saying
15:50 give me every other letter.
15:55 So think about maybe creating a game, gibberish game
15:59 that takes in a string as in a like it's a function
16:02 called gibberish, takes in a string and it just gibberi
16:05 called gibberish, takes in a string and it just gibberi
16:07 gibberish-izes it,
16:11 okay, it just like jumbles it up.
16:14 And if I do three here, you can see it stepping by three,
16:20 So pretty weird, but also cool at the same time,
16:23 So pretty weird, but also cool at the same time,
16:29 another thing that I wanna ask you guys as a practice to do
16:33 before I end this video is say I had the string hello,
16:40 I gave you the string, how would you reverse it?
16:46 I want, if I gave you hello, I want back,
16:52 Or if I gave you olleh,
16:57 you should give me back hello.
17:01 So hopefully, that blew up your mind on string slicing,
17:04 So hopefully, that blew up your mind on string slicing,
17:06 I'll try to put some exercises on clever programmer dot com,
17:10 so if you haven't already go enroll in to the school
17:13 so if you haven't already go enroll in to the school
17:16 and there'll be exercises and extra resources
17:19 that you can use to get help.
17:21 Also there are others in the community who can help you.
17:25 So good place to go for help,
17:27 but if you're watching on YouTube that's totally fine,
17:29 comment in the YouTube section below
17:31 and I will personally try to help you out,
17:34 other than that I'll see you guys in the next video.