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I want to talk quickly about file parts, because for some people, this might be a new concept.

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Up until now I wrote, let's say something like Sa'adat Pie or sad dot text.

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And I was able to run this code because when I ran it in my terminal or command prompt, there were

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all in the same folder on my desktop.

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If I do present working directory on a Mac, it shows me where I'm currently at, which is the desktop.

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So I was able to run it like this because my script file was in the same folder as my SAT and test text.

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But what happens if this wasn't the case?

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We can actually jump back a directory by saying KDDI, dot, dot.

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So if we go back, my present working directory is now user and I go, so I'm not on the desktop anymore,

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so that if I try and run Python three and then say script.

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Well, can't find the file, right, so let's go back to desktop.

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And try to figure out this problem, I'm going to for now make a directory.

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And call it, let's say.

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Well, a very generic folder or let's just call it at.

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So now I have an app folder.

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I can move.

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This sad text into the app folder now, so if I grab the sad text and move it to the app folder.

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If I go back now and.

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Try to access Saddat text, so let's say Python three.

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Script up by.

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Well, if I go back, I've appended Sadad text, so it's actually creating it for me.

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So instead, let's actually remove sad text because we actually have one already in here in the app

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instead of appending it.

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Let's just do a read.

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If I try to read now, I get a file not found.

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Er Saddat text doesn't exist because it checks the desktop and on the desktop we have nothing.

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We don't have said that text.

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So how can we get around this.

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Well I simply say that I want to go into the directory app Slash said dot text so that if I run this.

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Now it's it it's reading it, but it's an unsupported operation, so let's just turn this into a read.

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And we don't need any of this, so let's just.

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Read here if I run this.

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All right, it's working now I'm able to change the Forbath.

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Now, if you're on a non Unix based system, that is, if you're not on a Mac or Linux and you're on

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Windows most of the time instead of the slash, it's a back slash like this.

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So Windows and Unix systems have different file paths and file system in place.

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So this is something that you can read up on depending on your file path and why your prison working

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directory is you'll have a better idea of how it should look on windows.

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It's usually something like C and then backslash and then you'll have different file path.

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Now this is called a relative path.

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So relative to where I am, where I'm writing the script from, I am going to go from here into the

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app, into Sadaa text.

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I could have also copied this entire file path.

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And this is called an absolute path, so if I run this.

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This still works because I'm giving an absolute path, it's saying, hey, on this computer, this exists

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from the root user all the way into here.

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So this is another way of doing it.

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Most of the time you'll see relative because it's a lot simpler.

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Finally, you might sometimes see something like a dot slash dots simply means from the current folder.

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So if I run this, it's still going to work.

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It's going to say, hey, from the current folder, go to app folder, then go to the text folder.

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If I do dot, dot, slash like this, if I run this, I'll get an air dot dot means back a folder.

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So instead of our present working directory being desktop because we did dot dot will actually go into

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my user account and it's going to try and find an ugly slash app.

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Slash said text which is not going to find.

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Anyway, this is a bit of a tangent, but I want to let you know that these file parts are important

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and it's really dependent on a what operating system you're using, like Mac or Windows and also where

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you're calling the file from.

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Let's continue our discussion of files in the next video.

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One quick note that I forgot to mention, there's a really useful built in module in Python and you

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can see here it's new in version three point four called Path Lab. It's an object oriented filesystem

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path.

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Now, the main thing is you can see how to use it through the documentation.

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But the key thing is that if you're building a program that, lets say reads something from the file

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system, like a file.

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And this program can be used both on Windows and Mac and Linux systems, you want a way to make sure

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that it works on both, right?

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Because we saw how Mac and Windows have different file system with different slashes.

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Well, Pat, Leyb Library actually works with both.

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You can see over here if you want to manipulate Windows path on a Unix machine or vice versa, this

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is going to work for you.

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And it's a good way for you to create software that is compatible with both systems because Path Live

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is going to take care of the file pass for you based on what machine is running your code.

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Now, this is something you can read on your own and experiment, but I wanted to let you know that

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this does exist and it is a useful library for you to have in the back of your pocket.

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That's it for now.

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I'll see in the next one.

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Bye bye.