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I don't know if you have wondering about it, but we have a big issue with our program.

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The issue is that the user enters these to do items, but then if you close the program, those data

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are lost.

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So if I run the program again and I say show it shows nothing.

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And that is, of course, the expected behavior of the program, because we are trying to save the user

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data, the to do items in variables.

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The problem is that.

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When the program ends, its execution, variable values are discarded.

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Because they are simply saved in temporary memory on your computer while the program is up and running.

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So we need to figure out a better solution.

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The solution is to get the user input and store it via Python.

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In an external file on disk.

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And that is what you're going to learn in this video.

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So you're going to learn how to store data in text files.

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Now, there are different solutions to store user data.

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So one is text files, which is what we're going to use in this lecture.

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Text files is suggested to be used because it's a simple solution and it works very well with simple

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data.

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So in our case, we simply have these sentences.

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Now, if you had more complex data, you might want to use CSV format, so CSV files or JSON, and if

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you have even more complex data where there is more user interaction with the data, then you might

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want to go with the ultimate solution, which is SQL databases.

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So we're going to cover all these technologies in the course.

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Now let's focus on text files.

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So first of all, I would start by creating an empty text file.

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So to do that, you can right click over your project directory here.

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And go to new and go to file and give a name to the file, such as to do the pt x t, So that is a text

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file.

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Make sure that the text file is created in the same directory with your main AP file.

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So these are in the same folder.

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Then go to Maine that p y, and let's implement the ADD case first.

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So currently we have an empty list in here and then the user enters a to do item and we append that

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to the item to the list.

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So to do is update it at this point with a user.

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To the item.

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Now, we will keep these two lines as they are, but then we want to store the list items in a text

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file.

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To do that.

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You first want to create a file variable and this file variable, you want to store a file object.

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The file object is returned by the open function.

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So Open produces this certain type of object, a file object, just like we have string objects.

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That is a string object.

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That is a list object.

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We also have file objects.

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So these are designed to interact with files on disk with that file.

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So to interact with that file.

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This method requires the path to that file to dos the text.

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And then there is a second argument you want to specify, which is.

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A string again, It could be.

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W it could be.

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Or in this case it's w w means right and R means right.

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So if you want to write something in that file.

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Via Python.

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Then you write.

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W if you want to read the content of that file.

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So if you want to print out the content in via Python in the command line here, you want to read that

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file, so you extract the text from that file, store it in a python string and print it out.

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In this case, we want to write.

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So that will create a foil object.

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And then in that file object, we write lines.

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So write lines is a method available for file objects.

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And this right line's method gets as arguments a list.

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So our list is to deduce therefore the items of this list will be written into those the text.

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So let's try this.

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I'm going to run the script.

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Press add to indicate that you want to add an item clean.

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At again through and then exit to exit the program, press enter, and then we want to check to do that

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text.

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If you don't see anything, try to read, click here and go to real load from disk and that will refresh

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the content over to those that text file in your patch already.

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So these are the data we entered, not quite as you were expecting, probably because you see that these

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are merged together.

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There is an easy solution for that, though.

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You can simply.

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Add a backslash and character after this.

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So that part contains the user input.

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So clean, for example.

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So if you say clean plus that what you get is I can show you that in the console.

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So basically we're doing this clean plus backslash n.

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So that merges the two strings.

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But if you use print.

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And you do it again.

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Clean.

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Plus.

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RN and you press enter, then what you get is clean plus a brake line.

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So n is a backslash, n is actually a brake line.

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We didn't see the brake line here because if you just do clean plus backslash and python will print

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out a very raw representation of the string.

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So it it does not recognize backslash n as an actual brake line.

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But print is designed to convert that symbol.

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That is a special symbol, special string.

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It converts them that to a break line.

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So let's go back to our script.

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And here we are.

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This again.

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Add.

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Let's try to prepare this time and add again.

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Shower exit.

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Hmm.

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Let's check to do's.

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So prepare and shower.

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So now it is working.

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Well, these are.

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Each in one line.

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But there is a problem if you've noticed it, where it's clean and through.

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So they have disappeared.

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Why is that?

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I'll I'll explain that to you.

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What happens is that this line here, what it does is if it finds that file in the directory here,

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that's methods will override that file.

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So basically, it creates a new file with that name.

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Then it writes.

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The lists in that file.

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So if there were other items, other texts in that file, it will be overwritten by these new items.

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In this case, prepare and shower.

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So this is not the expected behavior we want for the program.

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We want to keep the existing to do items and be able to add other items under those two.

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So, for example, now we have these two.

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If the user enters code in the command line, code should be written in here.

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So let's go back and fix this.

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The way to fix this is to first get an item from the user and then create a list, a python list.

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And this list is going to contain the existing items from the text file.

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So first of all, we need to delete that list.

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We don't need that list anymore.

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So what we want to do is we get the item from the user and then we say file is equal to open.

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To dos the text.

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Ah, this time.

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So we open the file in red mode.

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We want to read what is inside that to do that txt file.

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And we create a variable to dos, which is equal to file that reads lines.

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So that is the equivalent of this.

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But to read.

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So it will read to the content that is in the file and it will create a list with that content.

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Each line will be an item of that list.

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So at this point, we have a list with two items and let me make a break line and then we append.

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The user's item in that list.

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So if the user enters.

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Clean than the lists at this point will be something like prepare.

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What else?

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Shower and clean.

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The item that the user just entered.

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So something like that.

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And then.

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Let me break this as well.

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And in this part, we.

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Creates a new file.

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So we completely overwrite the existing file.

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And in that new file we write that list which contains three items now.

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So let's try this.

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At.

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Play at.

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Fix.

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And exit press answer go to to do the text and that's the output.

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So we had to prepare and shower earlier.

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Now we have play and fix.

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So that's code.

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Make sure that.

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From the user to the items are stored in a text file.

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Before we close this video, though, there's something we need to add.

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So once you open a file object here and you have finished working with that file object, then you need

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to close it.

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Things will work even without closing it.

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But sometimes.

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Different parts of the codes can interact with each other in a way that.

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They will change the contents of your file if you have not closed it.

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So it's good that once you are done with the file, just close it.

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And the same goes for this other one here.

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Close.

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So you open it here, you close it here, you open it here.

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Finish what you do.

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You close it here.

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Now, this is just a variable here.

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You could also have another variable.

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Whatever here.

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So that would work.

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File whatever, file whatever that close.

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So it doesn't matter that we happen to have the same variable names in here.

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And that's about it.

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As a summary, let me open the Python console and show you what we just did.

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So we used the open function, and this open function creates a file, whatever.

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For example, the txt that is a path to all of the file.

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With W you create a new file.

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If the file is existing, it will be overwritten with an empty file and then you can write lines to

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that file by providing a list of lines.

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Line one.

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Line two.

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You execute that.

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Don't forget to close the file using the closed methods and a new directory here.

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If you do a reload from disk, for example, you should see whatever the text.

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So those are the lines.

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So again, you can override that file by opening it again.

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Right lines.

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And if you want to have brake lines between the lines at backslash.

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Inside each string.

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So that's one string.

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That's the other string.

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Backslash n press enter.

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File that close.

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Reloads the file on par charm and you should see this new output.

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It is also possible to write texts in a file, so hear the input.

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The argument is a list.

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How can you write a simple string?

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Well, that is also possible.

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Again, we use the open function and let's say whatever does whatever to the text in write mode.

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So the code is the same.

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But then instead of write lines, you use write, and instead of passing a list, you pass simply text.

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Hey, this is just text here and there.

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You can provide backslash and characters here as well and press enter and file dots close.

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It closes the file.

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This is the number of bytes written in that file.

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Just for your information, file close and to reload.

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Whatever to the text has this text now so you can provide.

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Here is the backslash which creates a new line.

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So that is how you can write text and about reading.

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The same goes for reading.

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So with open whatever the text in read mode and file that's read lines will return a list.

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So you see, it's a list file that close closes that file.

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Of course, you can also use a file that reads over whatever the text or over whatever to the text.

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And what you're going to get is one single string.

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So you see the difference.

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This gives you a list and the list has multiple string objects.

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One, two.

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While for the three, it gives you one single string.

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You can also see backslash n here, backslash n here.

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If you wanted to print out the backslash ends as.

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Brake lights.

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You want to wrap this inside parentheses and say print.

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So the print function gets this as inputs.

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Now, this is something interesting what happened here, and we didn't get any output.

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So perhaps you were expecting to see line one, break line, line two.

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That didn't happen.

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Even if you say five that read again, you get an empty string.

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That is because the rate operation is exhausted.

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So let me explain that to you.

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What happened?

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So we opened the file here in reads mode and then we read the content.

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Now there is something, a concept called the cursor.

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So when you just open the file, the cursor is at the very first position.

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But then when you apply the file that reads method, the cursor goes and reads the text and then it

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stays here.

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So after this method is executed, the cursor is here.

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Therefore, if you execute file, read again as we did in here, the cursor will try to read again what

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whatever is on the right side and down and there's nothing here.

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Therefore we get empty outputs here, empty outputs in here.

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So that's something to keep in mind.

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So the workaround is, of course, to close the file and open the.

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File again in red mode for the treat should give you those lines.

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So that's about this video.

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Being able to store data in text files and to read data from text files via Python is going to be very

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beneficial for many, many applications.

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I hope this was clear to you, and I'll talk to you later.