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Hello welcome to this tutorial on functions so a function is a block of code that performs a specific

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task.

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Python allows us to define functions according to our need known as user defined function and a python

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function may or may not have a name.

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And in this tutorial we will talk about functions which have a name

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and here does these syntax for defining a function and a function counters of two.

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But the head and the body function head the dot with Dickie Bird D E F which is the short form for definition

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and this keyword is followed by the function name and the function name can be any valid identifier

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and after the function name we have a list of arguments

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inside but and this is separated by comma and we use these arguments to parse required a data to a function

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and a function can take any number of arguments odd none at all.

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If a function doesn't take any argument then the parent misses is left empty the function header and

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the body separated by a call in here.

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After a debate and this is in the next line we have a block of statements or the function body the function

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body contains statements which defined what the function does.

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Remember all these statements in the function body must be equally indented.

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Otherwise we will get a syntax error as you can see all of these statements are equally indented Python

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uses indentation of statements to determine when blogs start and end

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the definition.

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The function definition ends there.

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The indentation ends.

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So as you can see with this statement The indentation has ended.

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So does the function definition the print statement he would

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is define out of the function.

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So here's an example off of user defined function.

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So I have used the key word D E F to define the function great.

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And this particular function does not take any argument.

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The parenthesis is left empty.

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Next in the function body I have a print function which prints the string hello.

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This is the function definition but a function definition does nothing by its an if we want to use the

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function.

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We must call it in order to execute the code inside the function definition.

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We need to call a function and the correct term is a function call.

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Here it is how you call a function your function name is great.

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And then you have deep it and this is and since the function greed does not take me any argument in

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the function call as well you do not pass any arguments to the function remember the function call must

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appear after the function is defined.

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You define your function first and then make a function called and you will encounter a name error exception

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you have your function call your ID and when a function is call the program control jumps to that function

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definition and executes this statement inside the function body.

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Once you make a function call the control jumps to this point in the program and after executing the

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body of the function the program control jumps back to the part of the program which going to function.

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So after all of these statements here and executed in the function body the control jumps back to this

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point in the program and it assumes execution at that point.

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Let us now execute the simple function in the Jupiter notebook.

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This is of a function definition as you can see here.

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The statement in the function body has been indented now in order to end the function definition the

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indentation should also end the next statement.

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Another example is a function call to the function greet call the function read using this statement

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here let execute the cell and decode inside the function greed has been executed.

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And here is another example.

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We have a function which takes two arguments a and b and within the function body we are adding the

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arguments a and b and assigning the result to a variable C and finally we are printing the value of

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debatable C and in the function call.

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I have parse the argument seven and eight execute this code in the Jupiter notebook function definition

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for the function.

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And we are passing the argument seven and eight to the function using a function called blitz.

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Execute this piece of code the function has added the argument seven and eight men.

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But in today's result no a function can also have an optional that don't statement.

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Up to this bind we have been discussing or creating functions which do not return any values and when

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a written statement is encountered inside a function the function terminate and the value of the expression

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followed by the the return keyword is sent back to the part of the program that call the function and

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the return statement can appear anywhere in the body of the function and the functions which returns

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why use are known as why you the daunting functions

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functions which do not return any values are also known as wide functions.

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So let's discuss an example.

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I have defined two functions the function and here takes in two arguments a and b and both of these

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arguments and returned the value nixed in my second function.

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Also known as + this function also takes two arguments A and B and D two argument but in this particular

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function we are printing the result.

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So what does it differentiate as we have discussed.

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This function is called O value the turning function and the second function is known as a wide function.

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We do not have the written statement in this function so let us define both of these functions in the

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Jupiter notebook and see the differences between value returning function and avoid function D function

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and which has the return statement.

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So let execute this piece of code.

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So the function has added to arguments and adorned the sum of the two arguments.

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Now let's also see an example of a wide function we want to define the function.

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And so this is the body of the function.

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We will now make a function call bypassing the argument forward and fight to this function.

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Let's execute this piece of code.

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The output of this function is 9 and the value added Dawn by the function and is also 9 in order to

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understand the difference between these two functions.

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Letters assign this function call in this scene to a variable see in this one line we are assigning

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the function card to a variable C meaning the value returned by this particular function is assigned

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to this variability C the output in this cell.

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Let's add another statement so we will use a print function to print the value of the variable C so

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let's execute this the value of the variability is nine.

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That means the result of this particular function has been assigned to this variable C and finally began

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C devalue here.

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Now let us check these type of the variable C

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the variable C here is an integer.

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This function good has returned an integer data type.

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Now let's go to this function which contains a print function in the function body here as well.

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We will assign a variable to the function called

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and execute this say the code in this cell.

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This function has been executed with this function call.

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And then the function body has a print function.

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The charge these arguments a and b as you can see the output here.

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Now let us check the type of the variable D which has been assigned to a function call.

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So let's check the data type of variable.

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The add function here which does not contain a return statement has returned the data type.

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None none the print function does not assign value to a variable and it doesn't return a value from

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a function called.

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So that is the reason the data type of this variable is of none type.

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Now let us consider another example here.

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We have defined a function test which has a written statement in the function body.

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There is no expression after the return keyword.

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So the expression followed by the return keyword is omitted.

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In this case the value none is returned by this function.

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So let's execute this cell.

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This particular function does not return anything.

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Let's assign this function call to a variable and then check the type of debatable x.

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So this is also the darned the special value none.

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Even if you have other done statement within the function body but if the expression is omitted the

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return value would be none.

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So consider another example here we have a function at 80 which returns the sum of the argument a and

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b.

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Now I want to use the desired of the value returned by this function.

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In short I want to multiply the result of the return value by minus one.

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So in order to do that I can assign this particular function call to a variable C I want to multiply

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the result by minus one.

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So the result is multiplied by minus 1 and then assigned to this variable C and then finally we will

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print debatable C here so let's execute this piece of code.

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The function D has added these two numbers A and B and then multiplied by minus 1.

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Assign this value to debatable C and finally printed this variable we can use the values written by

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a function in a program.

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Using this example.

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See this example here we have defined a function and and it returns this expression.

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And in the function call here we have two arguments.

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One is this value.

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And the other is the function at which is adding the numbers 2 and 3.

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A function can also parsed as a parameter in this particular function call D and function within the

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parents.

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This is executed first and the at dawn by D.

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Function is parsed as an argument to the function call.

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And here let let's execute this piece of code.

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So this is about the return statement.