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In this video, you learn to use Python methods.

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We're going to need to use a method to add to do this to a list, because currently in our program,

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all we do is get the two due from the user and then we print out that to do and that's all.

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We are not storing the to dos in a list.

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So I will delete these and add some code here which stores to dos in a list.

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You remember we did have some codes previously where we wrote a list.

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We created a list using brackets and then inside we add it to the one to do two and so on.

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So now, of course, we don't have to do once and to the tools, we don't have those variables.

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We have a to do variable.

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So to do is one variable, to dos is another variable.

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Two different variables to do now is added to the to do list.

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So let's print out to dos in here and see what we get.

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Run enter to do.

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Clean through.

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So this is the output we get.

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Let's try to analyze this to understand the problem.

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So while true executes this line first, so we get that output.

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The user enters clean and clean, goes inside the list.

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So to dos list is created and then it is printed out.

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So we print out to DOS here.

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So currently we have only the clean string inside that list.

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So far, so good.

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Then the loop goes back again to the first line of the loop.

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It executes again inputs.

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So we get this prompt again, we enter through and then.

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The second line is executed.

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To do so is equal to that list.

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What happens here is that this variable will override the existing to those variable.

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So the list we had with clean inside is overwritten by another list with through inside.

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So this entire line here overrides that existing list.

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And so we print out that new list with through inside.

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So obviously this here is not the solution.

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We want to delete that.

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What we want to do is first create a list outside the loop.

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To do is equal to this empty list, so Python will execute the first line.

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It creates this string, it creates an empty list and then goes to the loop.

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It asks the user for input.

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The user enters a to do, and then we append that to do in the to do list in that list.

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And we print out the to do list.

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So let's rerun the code answer to do clean through neat.

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So that's the list.

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As you see, the list is being populated with items in every iteration of the loop.

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So the program is working pretty well.

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We want to improve it further, of course, and we'll do that in the next videos.

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But now let's focus on the syntax we used here.

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You see this dot and then this.

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Key word is coming after that dot.

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This is a method.

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So methods are like functions.

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You see, this function has this parentheses and an argument, and the method also has parentheses and

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arguments, but methods are attached to data types to other objects.

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In this case, this append method is part of this to dos.

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Variable.

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Actually, it is not part of the variable.

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It is part of the object associated with that variable.

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In this case, the object is a list.

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You see, it's a list type and every object has its own methods.

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So for example.

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If you want to access the append method of the to to to do this variable is associated with a string,

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not a list.

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So if you try to apply append to that string, you're going to get an error.

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Let's try this.

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We run.

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Enter it to do so.

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Now we are here at this point.

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So Python has not yet reached the point where this append line is executed.

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So enter it to do like a clean press enter and you see that is an error.

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It tells you where the error occurred.

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So line seven, Line seven.

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Is this one in here?

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In part charm.

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You can also just click that to go directly to line seven.

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So that's a convenience.

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And so the cursor is in line seven now.

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You also get the line printed out in here, which has the error to do that the pants.

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And then this is a type of the error attribute error.

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HDR object.

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So SDR is the type of object, the data type that to do is associated with.

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So to do is associated with an SDR with a string object.

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So an object has no attribute append.

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So methods are also referred to as attributes.

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So a string does not have that append method.

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That's why we get this error.

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So how do we fix this error?

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Well, this is based on our experience as a programmer.

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The error cannot be fixed automatically by Python, so you have to take a decision because Python here,

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the interpreter which interprets our code is confused.

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So it doesn't make sense to append something to a string.

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It does make sense to append something to a list, but not to a string.

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A string could have different methods.

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Such as.

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Capitalize.

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Let's see what will happen now.

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Enter to do clean all use a lowercase string.

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Now press enter.

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So clean was printed out by this, but we didn't get any print out from this.

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So let me remove to reduce print to do so and execute again.

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You see, again, we will not get any print out.

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Why?

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Well, because we haven't used a print function.

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So if you want to see output, you won't use a print function as you see.

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Now, I put this entire expression inside the parentheses of the print function.

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Now, if I execute this enter to do clean, we will get clean with an uppercase C.

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So this method, it's capitalized is the first letter of a string and it returns the string with the

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first letter capitalized.

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So as you see, the difference between methods and function is that in functions, if this was a function

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which is not, it would get that to do as an input in here.

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It would be capitalized to do inside.

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But this is not the case and that is what makes a method a method.

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So a method to refer to an object using that dot notation and methods can also take arguments.

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So how do you know what arguments can a method take and how do you know what methods you can apply to

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strings and what methods you can apply to lists?

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How do you know what arguments you can pass to a function?

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So these are all questions which I'll answer.

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I'll give you the technique to answer all these questions by yourself so you can find the code you need

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by yourself.

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You'll see the list of methods you can apply to list, and you'll see all the methods available for

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list.

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You'll see all the methods that Python has available for string and so on.

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And I'll show you all that information in the video programming tool or concepts of today.

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So there is where you learn how to find the code you need.

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And here we end this video.

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So thanks a lot.

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See you.