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Hello welcome to this tutorial on built in functions in this tutorial.

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We will talk about the built in functions file input output print function input function.

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These built in functions are very important to know and will be used frequently while coding.

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Let's begin with the file input output function.

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Python has built and functions to create and manipulate files.

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Consider this function the open function this function returns a file object so to the open function

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you need to parse the file name as an argument.

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All other arguments are optional and have default values.

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Say for example if the file that you want to open is in the current working directory you can just provide

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the file name like this test dot the X D.

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If the file resides in a directory other than that you have to provide the full part with the file name.

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Make sure the file name and the PI given is correct.

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Otherwise we will get a file not found error coming to the access mode the access mode defined in which

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way we want to open a file if we want to open a file for read only write only or both say for example

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if we want to open the file for reading.

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In that case the access mode would be art.

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And this is the default mode if you want to open the file for editing that is for writing will be the

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access mode would be w.

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And if you want to add text to an existing file you can use the access mode it append.

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So I want to create a fly test dot the equity in the current directory.

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So I'm going to use this function.

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The open function if the file does not exist.

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This function would create a new Y in the right more we have to be careful with the access more w as

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it will overwrite into the file if it already exists.

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All previous data would be erased.

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So using the open function I'm going to create the file test data.

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Dot the extremes in the right mode.

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If the file you that you're going to create is in the current working directory you can just provide

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the file name like I did here.

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Or if the file decides in a directory other than that you have to provide the full part PDF file name

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using the open function.

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I'm going to create this file.

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So let execute this line of code.

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Okay.

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Next and this is the file that God created test data the 60.

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So we haven't written anything in this file yet so it is empty.

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Now let's close this and write into some text into this file and for that you can use the right method

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on the file object that we have here.

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So in order to do that on this object if you need to call the right method so let's call the right method

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and you can enter some texture.

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So I'm going to enter first line backslash in the backslash character can be used to tell the interpreter

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that the next character following this slash should be treated as a new line.

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Now let's and third a few more lines into this file if the dot right let's say second line and then

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one more line.

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All right so I have endured three lines in this fight.

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Let's close the file now.

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The close method helps to free up the resources that were tied to defining let us now open the file

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again.

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Here is the text that we have endured using the right method on the file object.

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Now let's add in more text to this file using the append method.

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The append method does not or what.

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The existing text in the file but keeps adding text to define it.

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So let's close this and open the file again since it is closed.

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Let's open the file again using the open method.

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So the file name is in court.

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That file name is test underscore data dot the 60 left open in the append mode.

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So we have opened the file in the access mode append.

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Now in order to write into the file we are going to use the right method.

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I am going to enter this text into this file and then finally I'm going to close define.

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After we're done let's open the file again.

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The last line has been appended using the access mode a next.

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You can also read what is there in a file using the access mode od which is read letters open this file

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in the read mode.

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So the file name is test data that the X T and then the access mode is odd.

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Now say for example I want to read the first four lines in the file.

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So I'm going to pass forward as an argument to this method read

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so as you can see the first four characters in the file has been retrieved.

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Now let's pass forward as an argument again to the Reed method.

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The next four characters including these spaces has been retrieved again call the deed method.

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The argument forward.

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Now let us not pass any argument to the deed method execute this line of code.

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So if we do not pass any argument to the deed method it reads all of the remaining text in the file

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from that the cursor is position.

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So this particular state Moon has a red beginning from where the court said his position to the end

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of the file if dot read.

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Now again if you try to read the file again it returns an empty string because the cursor does now at

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the end of the file.

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Now you can use the seek method FDR to seek to bring the cursor back to the 0 8 position so we can use

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this method to bring the closer to the specified position so I past 0.

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Now let's read the file again by passing the argument forward.

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It's gonna be the first four characters.

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Now if you want to know the position of the cursor you can use the tail method on the file and it shows

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that it is a D fourth position similar to the deed method.

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We have the read line method which added individual lines of a file.

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Let's call the read line method on the file object so it has read the first line from there D.

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Because it position to the end of the line that is the first line let's call the read line method again.

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So the entire second line is read so the second line is read from the initial to the ending position

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next.

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The next method is d e.g. lines method and this method returns a list of remaining lines of the entire

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file.

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So this is going to do it on a list of lines.

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So this is the third line which is one item and this is the fourth line which is the second item in

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the list.

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And then you can use a for loop to read the file line by line.

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And here is the code for reading each line from the file.

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The for loop is going to retrieve each line from the fine print the line.

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And finally after the for loop breaches of the file we are going to close the file using the close method.

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So let's execute this piece of code.

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This is how you can use a for loop in order to access each line in a file.