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Let's continue talking about methods and how they differ from functions.

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So unlike functions, methods are associated with a certain type.

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For example, strings have an upper method which will capitalize all the letters of strings.

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Strings also have a capitalized method which capitalizes the first letter.

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They have a title method which capitalizes the first letters of each word in the string.

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And of course, methods can also be applied to the variable which is holding the object.

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So in here we apply the method directly on the object itself, and here we apply it to the variable

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which holds the object.

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Either way, it's fine.

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But normally you work with variables when building applications, so most commonly you'll do this year.

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Now there are methods which return an output and methods which don't return an output.

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And this is a concept similar to functions functions which return outputs and functions which don't

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return an output.

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This method here title is applied to the greeting variable which holds the string.

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Hello there.

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Now, when you execute this code in a python console, you will get this.

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Hello there with h and PT capitalized.

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So this means that.

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This method is returning that string.

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Or you can also have this.

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Stored in a variable world is equal to a title and then print out the words and you'll get the same

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thing.

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Hello there.

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So the output of title is stored in this variable.

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In other methods, though, such as we have this append method which applies to the grocery list, so

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this method does not return an output.

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So if you assign a variable here, such as variable.

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Equal to that variable will be equal to nothing because no value is returned from the append method.

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However, the append method.

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Modifies its object.

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A method modifies its objects when the object is mutable.

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So lists.

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All lists are mutable.

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Strings are not mutable.

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So if I print out groceries here, you'll see that apples have been has been added to groceries.

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So groceries was a list of three items up here.

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But then here it became a list of four items.

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Similarly, we can apply a sort method to groceries, so this sort method will not return an output,

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but it will modify its object.

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So this is not the same as the title method tied to the returns and output, but it does not modify

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its object because the object here is a string and strings are immutable.

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They cannot be modified.

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If you really want to modify a string, you'd have to store the new outputs in new variable.

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For example, creating new is equal to that, and then creating new will be the new string with H and

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T capitalized.

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But it's a new object, right?

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You are not modifying the existing object which is currently connected to the greeting variable.

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Right.

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That's about methods which apply to mutable objects and methods which apply to immutable objects.

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To get a list of methods for a particular object type, you can use the function.

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For example, for strings, you can do SDR and you'll see that, for example, you have the lower methods

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here.

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The title method which we used, also the upper method, etc..

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Alternatively, you can also apply deer to an instance of strings.

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So hello is an instance right?

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SDR is the class which represents all strings.

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So a class is like, for example, let's say here we could say human.

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And so the human is the class, right?

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But then if you refer to a particular human which has a name and he lives somewhere or she lives somewhere.

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He has an identity and so on.

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That is an instance of human class.

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So the person, one particular person is one particular instance and the abstract concept human is the

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class.

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So the same goes here as the R is an abstract concept and hello is one instance of that concept.

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Of course, you can apply deer to other object types such as list.

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This could be int as well.

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Float, etc..

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How to create new methods.

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So for function, for example, we have functions which we access from Python, for example, the print

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function of the input function.

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But we can also create custom functions using the dev keywords.

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Now, with methods we have these methods for example operand and title and append.

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But how do you create new methods?

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Well, since methods are connected to their object types, then first you need to know how to create

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object types, right?

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How to create a human blueprint.

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For example, how to create string blueprints.

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That is something you haven't learned yet.

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But you learn that in the second half of the course, that's an advanced concept that the ultimate level

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of python you can get.

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So once you know how to create these types object types, then you also learn how to create methods

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for these types.

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So perhaps you can create an app, a booking system for airplane tickets, and you'd have like a ticket

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class, A ticket type.

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We should create ticket instances for customers, and then this ticket class could have a cancel method

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which cancel the ticket or a delete method which deletes the PDF ticket or it deletes the ticket from

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the database and so on.

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Lists and tables.

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So that's a list.

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That's a table.

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What's the difference?

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Well, temples are immutable.

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So, for example, you cannot have an append method for this value staple.

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You'll get an error if you try to execute that because the append method is meant to modify.

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The object it applies to.

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But tablets are immutable, so this will not work.

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Usually lists are used when you want to store homogeneous items.

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For example, this list contains strings only.

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Even though you can store various types, but usually you want to use lists for homogeneous items and

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you also want to use lists when you foresee that during the course of the program.

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In the program.

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During the execution of the list may be changed.

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New items can be added to the list and so on.

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That is something that you will better understand when you build real applications throughout the course

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and tuples.

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Are more meant to store heterogeneous items, for example.

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Let's say you have a web app where the users can upload an image and they want it resized and they want

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it grayscale.

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So they may input some numbers in input boxes in the web app interface.

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And so in the backend in Python, you will get those numbers in a tuple, you might get the grayscale

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string.

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So the user is saying that I wanted grayscale and I wanted a jpg.

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So you may store such data in a tuple.

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Right indexing.

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You can use indexing on strings, lists and tables.

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For example, Grocery Zero will give you the first item off the grocery list.

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Groceries, too, will give you the third item.

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So 012.

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That's at the third item.

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The same goes for tuples, so that will give you great scale.

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The third item for strings as well.

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So.

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And is the third item with index two.

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And we also have negative indexing.

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For example, minus two will give you a this because our is minus one, A is minus two, minus three,

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minus four minus five and so on.

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You might want to use negative indexing when you're accessing items which are closer to the end of an

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array array, I mean at least to pull or string.

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Also called sequence.

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So these are also known as sequence types.

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Of course, this is a string type.

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This is a list type.

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This is a type of type, but they fall in the category of sequences.

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So that's how you access individual items, but you can also access a slice by using that column symbol.

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So that will give you the items from index one up to index two.

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So the item with index three is not included in the slides.

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So you only get 1080, which is this.

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So zero one index one and index to grayscale.

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So that's the rule for indexing.

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It works for strings and lists as well.

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Then we have negative indexing.

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Minus three, minus one means.

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From here, which is minus three.

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Up to here, which is before minus one.

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So always the second index in the slides is not included in the slides.

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So index three was not included here.

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Index minus one JPG is also not included in this slides.

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Lastly for this video, let's talk about dictionaries.

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You should use dictionaries to store your data when your values are more heterogeneous and it's important

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to have labels on them.

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So the data here are, for example, John Smith for it.

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And so these are heterogeneous because these are strings, right?

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And this is a number and the labels are first name.

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So this tells you that John is a first name.

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Then we have last name.

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So Smith is the last name.

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And then we have age, which is 40.

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So.

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These are known as keys.

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First name is a key.

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Last name is a key.

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And.

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And age is also a key.

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And the values of this dictionary are John.

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Smith and Foley dictionaries can also be insight other items such as lists, for example.

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Here, this is a list.

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It starts in here and it ends in here.

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You see the square brackets.

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So this list has three items.

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That's the first item.

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That's the second item.

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And there's the third item.

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So each item is a dictionary because at least can have any type of object.

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And dictionary is also an object, just like we have strings and integers and floats, etc..

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So this structure here would be appropriate if you had multiple persons.

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So you would store data about those persons and you'd have the same key in all the dictionaries but

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different values, for example, John here Smith and the H, and you repeat that information but with

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different values, right?

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So that's one way to store these data, data about persons.

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However, in certain applications, depending on the scenario, you may want to store those data differently.

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For example, here we also have data about persons, but this will be a dictionary.

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So it's one dictionary.

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It starts here and it ends in here.

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And then this dictionary has keys and values.

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So the keys are the same.

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They are just strings first name, but the value is a list.

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So the value of each key now is a list instead of a string.

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So this list here has the first names of all the persons.

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And then we have another key, which has also the last names of the persons and the age.

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Which one is better?

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Well, there's no answer for that.

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Whether this is better or that.

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So it depends what you want to do with these data.

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Do you simply want to print them out or do you want to modify them?

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That is something that you realize as you build the application.

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So nothing to worry about.

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Now what is better and what is not?

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And lastly, to access the values of a dictionary.

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You use that syntax, so you refer to the variable which holds the dictionary.

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John In this case.

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And then in square brackets you refer to the key in quotes.

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So that will give you Smith the value of the last name key of John Dictionary for this here, which

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is a list you'd first have to do too.

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So with that, you'd get this dictionary because this list has three items.

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So that has an index of zero, that has an index of one and that has an index of two.

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So with that, you get the last dictionary, and then from that dictionary you access the first name

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key.

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So that will give you some.

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That's what we get here, SIM.

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Since this is a dictionary, first you have to give a key.

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So here you give a number because that was a list.

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But here you have to give the key of the dictionary first name and then this up to here.

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You will get the list as outputs and then out of that list you access index to.

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So the item with index two, which corresponds to SIM.

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So you get SIM as outputs.

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That's above this video.

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We have some more.

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So you in the next one.