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Hoping that you are enjoying the videos.

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Let's start with the very first video on this series of revisions reviewing the basics of Python.

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So I'll be showing you coats here.

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And you have two choices.

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Either you can just watch these videos without doing anything, or you can start a passion project and

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then write the code either in that P files.

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Or just use an interactive python console.

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On my end.

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I have placed the code already in something called Jupyter Lab.

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So what you're looking at is a tool called Jupiter Lab.

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In Jupiter lab, you can write in code and execute it both.

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That is something that you learn in day 30.

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So Jupiter Lab is good for presenting out code to other people.

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So for now, you don't really need Jupiter lab, so please focus on Python code.

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Right.

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Let's start with the first concept objects and variables.

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So we have two main topics and these topics have subtopics so objects can be stored in variables.

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Writes John is an object, Smith is an object, and this number here is also an object.

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All these are strings, actually.

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So everything that is wrapped in double quotes is a string, even when that is a number.

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So these are actually real numbers.

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This is an integer and this is a float.

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Now you'd ask, How do I know when to use codes on a number and when to use the number without quotes?

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Well, the answer is that if that number has mathematical meaning.

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Then you should use the number without quotes.

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But if that number will not be used in mathematical operations such as addition or multiplication,

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etc., such as is the case of the ID here, then it should be a string.

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So all these here, all these objects drawn and five and 1.75 are stored in variables.

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But sometimes.

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Objects can be produced by functions.

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For example, we have this variable here, and this variable is associated with the call of the input

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function.

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So when this input function is called, when it's executed, then the user will enter a string, for

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example.

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Or did.

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This string will be stored in that name variable.

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So this is indirectly.

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In this case we stored the objects directly in the variables and here is indirect.

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So when we call that variable, when we print it out or you just call it in the interactive shell,

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you should get something like this.

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So that's the string that was stored in the name variable.

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Sometimes, though, you have to be careful with types.

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Let's see this other example.

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This is asking the user to enter the hearts so the user enters the height.

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And then this height is stored as a string.

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So this is not what you might want here, because this has some mathematical meaning.

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It could be subtracted or added to another number.

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So in that case.

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You can use converters such as a float or int.

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So in this case, this is the same code as this.

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But in addition, we have this float with parentheses here and parentheses there.

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So whatever the user enters here, that will be converted into a float.

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As you can see here, name is one 75.0.

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So that brings us to the next topic, which is functions.

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So that was a function.

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Input was a function.

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Print is also function.

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Now not all functions return a value.

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This is something that you really should understand.

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For example, the print function does not return a value, right?

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So in the case of the input function here or here.

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The input function returns a value which was 175.

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That value is stored in the name variable, but some functions such as the print function does not return

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a value.

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Right?

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So in x, if you print out x, you'll get nothing because there is nothing stored in x.

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This, however, doesn't mean that the function isn't doing anything, so the function might still be

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executing some procedures.

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For example, printing out some texts on the command line.

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Right.

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As is.

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As is the case here.

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But don't confuse that with.

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The returned output.

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Let's take another example with custom functions.

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So that is a function which you can create, and this particular function is indeed returning a value.

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So this function is basically similar to the input function in that it returns a value and the value

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is returned with this return keyword.

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So when you do foo, so the name of the function, when you call that function and you associate it

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with a variable in x, you will store whatever you return in here.

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So x will be equal to ten.

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But if you write another function definition which doesn't have a return statement.

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So no return statement here.

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And then you call the function and you try to store the output in x, then x will have nothing associated.

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Well, in some terminals, in some consults, perhaps you get a non printed out, which is some kind

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of value.

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Actually, it's a kind of object type.

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Like we have strings, we have numbers.

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This is also a type of value, but it means that it's a nothing value.

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So make sure to return a value if you want the function to give some output.

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So that brings us to the issue of return versus print.

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So this function here for one has this value variable declaration, and then it returns that value.

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It should be value, not ten.

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So it returns ten basically.

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And this function here, instead of returning it prints out the value.

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Now to understand the difference between that and that.

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You should call the function.

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So let's call the first function.

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For one, we store its output in x one and x one will be equal to ten.

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Right?

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Because it returns this value here which has a value of ten while x two is equal to four two.

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And no notice that if you do this, the function through two is being called, and when the function

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is called print is executed, that means you will get an output when the function is called.

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However, in here we didn't get an output when foo one was called.

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You don't get an output because there is no print function here inside this function, so nothing will

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be printed out.

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However, the difference is that the first function will store a value.

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In x one, you see x one will be ten, but x two here will be equal to nothing.

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Right?

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So that is the difference between return and print.

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Functions can have parameters.

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So these functions here didn't have any parameters.

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So the parentheses are empty, but this one here gets a parameter and it processes.

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That's parameter and it returns some results.

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And then.

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You can call that function by giving a value to that.

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Parameter or now you can call it an argument.

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So when we're talking about the function definition, we usually refer to that as a parameter.

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But then in the function call, we refer to that as the argument.

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So a number is the argument and ten is the value of the argument.

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So the function will get the value.

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Ten It will.

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Do ten times ten 100, and it will return 100.

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So 100 will be stored in x.

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So x is 100.

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Now, this here was a function called with an argument name, and this year is also a function called

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but without the argument name.

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So these two produce the same results.

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But the way you declare the argument changes.

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So it's just a change in the style of the code.

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The functionality doesn't change.

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Which one should you use?

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Well, both have their advantages and disadvantages, so this year tends to be a bit more readable because

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you know that ten is the number arguments.

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So you know what ten is and this year is shorter, so it's cleaner.

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So you have to choose between shorter codes and cleaner codes.

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And usually if it's clear what arguments you are passing to a function.

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For example, if this was a function that says calculate.

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Square.

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Then you know that this function is calculating the square of a number so you can just pass ten and

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you know that you are calculating the square of ten.

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So that's the idea here.

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Then we have functions with multiple arguments so you can pass multiple parameters in the function definition

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divided by commas, and then you can call those parameters, those arguments.

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Again, you can either do number one is equal to ten or number two is equal to 20.

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Or you can just pass the values without the argument names.

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But be aware that if you pass the argument values only, you should respect the the older of the parameters.

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So ten will go to number one and 20 will go to number two.

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Right.

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Functions with default parameters.

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So this here is a default parameter.

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It has.

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A default value, which means that when you call that function, which is what we're doing here.

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And you are okay with that argument.

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Having that default value, which is true in this case, then you don't have to pass that argument in

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the function call.

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But if you want to pass that argument, then you can do so as I've done it here.

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Right.

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That was own objects and variables and functions.

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In the next video, let's talk about methods.

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See you there.