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Now,

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in the last lesson, we saw how to get up and running with our brand new Flask

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server. In this lesson

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I want to take it back a little bit and talk briefly about some of these

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commands that we put into the terminal here,

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because the terminal is actually a really powerful tool.

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And it's something that's also referred to as the command line and its a way of

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typing in commands one line at a time in order to control our computer.

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The command line is also known as the shell.

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So what exactly is a shell?

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If you think about your operating system as a pistachio nut,

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then the kernels of the actual pistachio, the thing that you're going to eat,

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I'm really sorry about all the food analogies.

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You can clearly tell I'm pretty much hungry most of the time when I'm recording

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these videos, but let's get back to the topic.

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So if your operating system is a pistachio,

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then the actual nut is the kernel. And in computing

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the kernel refers to the actual program that interfaces with the hardware.

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So it's the core of your operating system. Now,

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the shell of your pistachio or the shell  in computing refers to

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the user interface for you as a human

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to be able to interact with the kernel and in turn with the hardware of your

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computer. And there's two variants to the shell.

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There are graphical user interface shells, so for example,

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when you open up finder

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you're using a graphical user interface to access and find your files.

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But there's also a command line interface

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which is what we're going to be talking about and what we're going to be

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learning about in this module.

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So this is an alternative way of interfacing with the kernel.

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Now it can seem intimidating at first,

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but I want to show you that it's actually super simple.

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And once you understand it, you're going to see that it's actually really,

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really useful tool at your disposal.

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A lot of the things that you can do with command line can be done using the

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graphical user interface. So why use

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the command line at all? At the end of the day,

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what it all boils down to is about greater control.

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And in your journey of becoming a better developer,

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you will need to understand and exert more power over your tools,

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that is the computer hardware. But on a more day to day basis,

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you will find that if you're a regular command-line user

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that it's actually easier and faster to do a lot of really common things.

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If you're a Mac user, you've actually got a dedicated terminal application.

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So if you go to spotlight and hit the search button and look for the terminal

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and hit enter, you can see that this is the actual terminal application.

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Now I've styled it up to look a bit more like a hacker because I like scaring

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people in Starbucks, but that's not the only you can change.

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You can change the color of your terminal,

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you can also change the type of shell you're using. Currently,

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if you are running macOS Catalina or above, so Big Sur

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or any of the future operating systems, you're going to be using zsh

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which has now the default Mac shell.

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All right,

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Now, if you're on Windows however, the default shell is the command prompt.

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So if you type in to search for the command prompt, you can see

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this is the app you need to launch and this is your command prompt.

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For the most part, you can type in the same commands on Windows and on Mac

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and it will work on both.

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I want to show you some common things we can do in the terminal. Here

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I've got my terminal and the address of the terminal is determined by the part

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that's just before the prompt. So at the moment, it's a ~ on my Mac.

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There's a couple of things I want to show you that you can do with the terminal.

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The first thing that's really useful to know is where am I in my file path?

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And to do this, we have to write pwd, print working directory.

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And this tells me where I am. Once you open up your finder

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as you can see up here, go to view and then go to show path bar.

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And this is showing us the path from our hard drive/ users/angela,

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which is exactly the same location as what I've got now in my terminal.

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So the print working directory is really useful for you to locate where you are.

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Similarly, on Windows, you can see when I do print working directory,

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it tells me that I'm in the C:\users\username.

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So C drive, users, username... right here.

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The next command that is really useful is ls,

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which stands for list.

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And what this does is it will list all of the files and folders at your current

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working directory.

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So it's going to list everything that's in this current location where I am at

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basically this. So if I go ahead and hit enter,

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you can see all of the same folders showing up as it does

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in finder. Pwd and ls are really useful for finding things out, for displaying

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things.

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But we can also use the terminal to move around in our computer.

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And we do that using the CD command, which is changed directory.

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So if at the moment, my working directory is users/Angela

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and I want to get into my desktop folder

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which is clearly one of the folders that I can access, then I can simply say

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change directory to desktop. Now,

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one of the things you can do to prevent yourself from getting repetitive strain injury and

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typing a lot is you can type the start of the folder, so for example desktop-

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De and then hit tab,

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and it will narrow down on the possibility that you can go to so there's

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development or there's desktop.

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So if I add one extra S and I hit tab,

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it's now going to automatically insert the folder that I'm looking for,

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which is desktop. So now if I hit enter,

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you can see that this part before my flashing prompt has changed and it's

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changed to the desktop. So now, if I do pwd,

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you can see I'm now in users/angela/Desktop,

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which is the equivalent of double-clicking on this basically.

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Okay.

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On my desktop what if I wanted to create a new folder? Well,

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we can do that using the make dir or make directory command.

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So we're saying make directory and then we give it a name. So let's say

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I want to call this Test then I'll just say mk

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dir Test. And notice the location while you are at.

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So I'm going to be making this test directory on my desktop.

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And as soon as they hit enter, there you see it.

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It's created that folder from scratch.

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So now here's a question. If you wanted to navigate into Test so that when you

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print the working directory,

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it's going to output users/yourusername/desktop/test.

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What would you do? What would be your command? Pause the video and

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have a think about that. Alright,

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of course, we have to change directory coz at the moment we're in the desktop

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which is this, and if we want to go inside this test folder,

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then we have to cd into it. So cd into test,

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and now we're inside the test folder. And if I hit pwed, you can see

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this is where I'm at. Now,

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once I've cded into this new directory,

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I'm going to create a new file in this directory. To create a new file

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the command is a little bit different from creating a new directory.

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The key word is touch. And after the key word, there's a space

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and then we can provide the name of our file.

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So let's say that we want to create a new Python file

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which we'll call main.py. Now,

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what it's going to do is create this file code in main

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which is a Python file and it's going to do that inside the Test folder.

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So let's hit enter and there you see it.

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There's our Python file created without any clicking or dragging completely done

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with our command line. So we've seen how we can create folders,

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how we can create files. And by the way,

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if you want to create a different type of file that you just change the

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extension. So it could be .text,

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or it could be .docx or whatever file format you want to create. Now,

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what if we wanted delete our file? Well,

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all we have to do is make sure we're in the correct directory to be able to

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access that file. So when we hit ls,

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we should be able to see the file we want to delete.

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And then all we have to do is type rm which stands for remove

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and then we could put our main.py. So there it is, it's gone.

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Okay.

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Now, what if I want to delete the Test folder? Firstly,

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I have to navigate one step up. Instead of being inside the Test folder,

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I can't delete the Test folder while I'm inside the Test folder.

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I have to go one step up, which is the desktop folder.

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Now of course I could say cd into the full path

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which is /Users/angela/Desktop.

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Now this would work, but this is really wordy.

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A really simple shortcut for navigating

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just one step up is writing cd and then two dots.

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This is going to take us to the parent folder, which is now Desktop.

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Right.

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From here I'm going to delete this folder. Now to delete a folder

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we can't just put rm. We also have to put a flag.

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So a - and then rf. So this is going to recursively, forcibly, remove this

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folder that we're going to add here, which is the Test folder.

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Now the thing you have to be really careful about rm -rf is it does things

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recursively. So if there were lots of folders inside this Test folder,

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then it's going to delete everything in there.

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And if, God forbid, you actually have this and you put it onto your whole computer,

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well then that's going to be a real disaster.

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Because the thing you have to know about the terminal is that it's a very

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powerful. And what did Spider-Man's uncle say? With great power comes great

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responsibility.

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There's some pretty funny stories about people who accidentally deleted

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everything on their computer just by messing with rm -rf.

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So be really careful that you are in the correct location to delete the folder

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and to double check that it's the right folder.

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Because when I hit enter,

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you can see it's not going to ask me for a confirmation

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and it's also not going to put that folder or the containing files into the bin.

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So be really careful when you're using the terminal.

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There you have it.

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There's an introduction to the command line using zsh on a Mac and using the

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command prompt on Windows. Now,

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when you open up PyCharm and you go to this emulator terminal,

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so it's a sort of application within an application,

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you can see that it looks pretty much the same.

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Basically, all that PyCharm's done is just bundled the command

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prompt into the PyCharm on windows and the zsh terminal into the PyCharm 

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on Mac. So you can do everything that you can do in the terminal

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inside PyCharm as well

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which makes it really easy to pip install modules or to run our Flask server.

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Now,

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if you want to know about other things that you could do in the Windows command

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prompt or the Mac terminal, you can simply just search for command prompt

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cheatsheet or terminal cheatsheet.

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And what it will take you to are lots of addresses

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which contain basically a lot more things that you could do with your command

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line. But the ones that we've talked about today

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are some of the most common ones and 99% of the time,

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those are going to be the commands that you're going to be sticking to.

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So write them down if you need to review them regularly.

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And if you just use them on a regular basis,

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you won't have any trouble remembering them.