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Hello, dear friends.



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So something must have caught your attention since our first couple of lessons.



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Hmm.



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From the very first moment, we always talked about the concept of function.



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And moreover, in the code we wrote, we we used this word function.



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Well, what is the function?



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Break it down for me.



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All right.



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Let's have a look.



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Now is the time.



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So what is the function?



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So functions are structures that have certain functions in programming that we use repeatedly.



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For example, the function of the print function, which we have used since the very beginning of our



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works, is to print the values that we send onto the screen.



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So why do we need to use it?



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The task of the function is to bring together complex operations and it'll enable us to perform these



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operations.



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Boom in one step.



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For example, the print function was written once by Python developers.



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And we can use it again and again and again and again in different parts of our programs.



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So it's by using functions that we can combine one or more steps into one name.



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The function only runs when it's called Just Like My Dog.



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Now, are there any more built in functions in the Python library like print?



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That's right.



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Python gives us many, many, many built in functions in his library.



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But we can also create our own functions.



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So how do you create a function and how do you use it?



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All right.



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Let's see by example.



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Let's define a function named some with death as our key word.



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And give two parameters, A and B.



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Now, at the end, we do have to put a Colan mark.



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And now we can use here a docstring.



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Wait, here's another one.



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What's the docstring?



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All right, docstring specifies what the function does.



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It's optional.



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If you want to, you can add it.



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If not, you don't have to.



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It's not necessarily necessary.



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But if a different programmer wants to use your functions, they'll be able to know what the function



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does.



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Get it.



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Cool.



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Now let's continue.



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Here we take the functions task print A plus B.



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Now, are functions ready?



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So let's try some for five.



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The result is nigh.



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Oh, way simple right now.



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That's not all we've got here.



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We can now talk about return statement and functions.



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So what are return statements then?



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The return statement means that the function returns a value to the place where it was called after



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the operation.



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OK, I'm going to read your mind again.



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So why do we need to use it?



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Because we can store the value that we receive in the function in a variable and use the variable elsewhere



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in the program you follow.



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I'll give you an example.



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We define a function named sum and give it four parameters.



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The task of this function is this summer to give an argument, right?



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Now we define another function named multiply and give one as a parameter to it.



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Now, the task of this function is multiplying the argument with two.



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So as you can see, both the functions will work smoothly.



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But what if we want to use the result of the some function as an argument to the multiple function?



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Yeah, we're going to get an error.



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So at this point, what if we use a return statement?



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That's how we get it.



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Let's try it.



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Def some parenthesis a, b, c, d, parentheses.



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Colon.



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Return A plus B, plus C, plus D.



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Death, multiply parentheses, a Prentice's colon.



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Return a asterisk to.



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Multiply.



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Some.



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Parentheses.



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12, 14, 13.



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Because Brent says.



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The result is 98.



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Did you do that in your head, too?



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But that's it.



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You got it.



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All right, so are you ready for another one because we got one more topic and functions.



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It's called the lambda expression.



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All right.



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So what is the lambda expression?



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It's also called an anonymous function.



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Now we can define it with lambda expressions.



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So what's the difference then, between normal functions and a lambda expression?



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I'll tell you with a LAMDA expression, we can define a function in one line, lambda expressions can



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be used, especially when it's troublesome to write a short function with def.



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So Lambda function can take any number of arguments, but it can only have one expression.



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Get it.



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So the power of Lambda is better shown when you use them as an anonymous function inside of another



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function.



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Oh, OK.



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So how do we use it?



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Let me show you.



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As you know, in Python, we define a function with the deaf statement.



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Deaf some princes, a, B, princes Colan return A plus B.



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So this function aggregates have parameters given to each other and then returns as some of them some.



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10 14.



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The result is 24.



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So if we want to do the same with the help of the lambda function, how do we proceed?



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Watch closely.



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Some underscore one equals.



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Lambda.



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A B, colon, A, plus B.



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Some underscore one.



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Princess 10.



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Fourteen close friends.



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The result is 24.



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So Lambda functions are one of the advanced functions of the python programming language.



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And you just cracked the code.



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So that's it in this lesson, we have learned the function logic in Python and how it works.



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But we also talked a little bit about the return statement and the lambda expression.



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So we're going to put a few of these things together in the next lesson.



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I want to see there.



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Have a nice day.