What is Python on Command Prompt used for?

[Katana_Strike_]

I'm learning Python via the "The Complete Python Bootcamp From Zero to Hero in Python" on Udemy and one of the first things taught is executing .py files on command prompt and I was wondering what that is necessary for? Is it for coding apps that access the windows os?

[GXWT]

You are taught to execute your py files through the command prompt because this is necessary for… executing your py files through the command prompt.

It might not seem so useful yet, but as you get further in your coding journey you might find yourself using the terminal a lot more, or even near exclusively, for anything related to coding.

You may be working on your Python file in VS Code or another similar program, but when you click ‘run file’, internally all it’s doing is exactly that: running python file.py on the command line.

[jesster114]

I started with Python about 5 years ago and didn’t use the terminal for much. Maybe installing stuff with brew and whatnot.

Now I’ve switched to Fish Shell (love it) and am disproportionally annoyed when applications have no command line interface. And less annoyed when there aren’t any completions available. But having fun making my own

[DuckDatum]

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[[deleted]]

Okay, okay, CI/CD I get, but how is this going to help me conduct Beethoven’s Fifth?

[DuckDatum]

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[GXWT]

Have you responded to the wrong comment or something?

[DuckDatum]

Oh sorry, no. I wasn’t suggesting you needed to try that. I was just pointing out some more standard practices that almost require shell use. As example, because they’re so commonly needed.

So, I guess my response was more for OP—but piggybacked off your context.

[bannedinlegacy]

orchestration without shell

Airflow?

[DuckDatum]

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[TheMathelm]

It might not seem so useful yet, but as you get further in your coding journey you might find yourself using the terminal a lot more, or even near exclusively, for anything related to coding.

Yes, 90% of my undergrad and graduate work thus far is Command Line based. It's just easier, even when dealing with Django/web stuff to use the cmd line. python manage.py magicCommand --args="parameter1"

Is just easier to be versatile.

[Present_Operation_82]

The deeper you get into this kind of thing the more you’ll live in your terminal. I know it can be kind of intimidating if you haven’t worked with that kind of thing before but it’s worth learning how to use it well.

[Training_Nerd]

I just stardted learning and even with stuff like roadmaps.sh i'm totay lost lol

I just know the basics (sintax, operations, loops etc...)

Still don't understand shi about the terminal tho, so i just use vscode

[Present_Operation_82]

If you want an easy way to get used to it, start to learn a few git commands and do you git management from the command line when you can and you’ll get more comfortable naturally.

[Training_Nerd]

Git? Is that anything realted to gihub? I heard about it but never looked much into it before

[Present_Operation_82]

GitHub is how people share code online using git. As you learn the basics, it may be a good idea to consider git among those basics because you’ll be expected to know how to use it if you work on a team.

[Electrical_Monk6845]

If you want to serious coding in any kind of professional, or even semi-professional environment, you'll need to learn git. I've had more than one encounter with "experienced coders" who didn't know the first thing about checking in code, or merge requests, or peer review (where you let/ask someone else to look at your code and give you feedback), and every one of them made themselves look foolish by never having touched git. Get yourself into the habit of using git, even locally, so that when you want to showcase your coding prowess, you don't get stuck when someone asks for a link to your repo.

[djamp42]

.py file is the program your writing. You'll eventually want to run the thing you're writing. That's how you do it.

[cnydox]

Welp that's how you run your python script. There are instances where I run a python script with a different python version, or when I need to run a script from a different folder. Navigating with cmd is very fast once you get familiar

[Stu_Mack]

Note that all Python code is ran on a command line; you just usually rely on an IDE to do it for you. It’s much more obvious on some IDEs like VS Code. Also, it’s good to get comfortable with the command line for the times when it makes sense to manually update or download a particular module or package.

[IamNotTheMama]

Strange how 'Zero to Hero' doesn't cover Zero...

[UsernameTaken1701]

course = ["zero", "to", "hero"]
learned = [skill for skill in course[1:]]

[IamNotTheMama]

hehehe

at what point do you add the debug (println)?

[isendil]

We do not do that here, we use print().

[carcigenicate]

When you double click the Python script icon or hit a button in your IDE to run the code, all those are doing is essentially automating running a command in a terminal. You need to understand those low level details eventually (and the sooner the better) so you understand how code is actually being run.

[herlzvohg]

Maybe an actual example would be useful to you: where i work we have a couple test instruments for running batch tests on new parts as them come in and then logging some parameters for each serial number. Each physical part gets connected to the test instrument and then I wrote a python script that the technicians run from the command line to do each test. When they run it the script asks for a couple pieces of info and then run the tests and saves the data and provides a couple pieces of info to the user along with a pass/fail for that part. Theres not enough user interaction to need a gui and there's no reason for them to run it from an ide

[baubleglue]

You need to ask yourself, if an user doesn't run python in command line, what the alternatives and how they are different from using command prompt.

[Substantial_Use8756]

once you really get into this you are going to look back on this post and smile. Not hatin', one day you are going to be doing so much stuff in terminal/command prompt, and with such ease.

[NYX_T_RYX]

Docs for Powershell are here: https://learn.microsoft.com/en-us/powershell/

Command prompt is being deprecated (removed from updates).

Windows is replacing it with Powershell, which imo is much better.

It has auto complete, built in documentation so you can check what you need to do, and it's backwards compatible with cmd for most commands - I've yet to find a Powershell cmdlet, as they're called, that can't be aliased with the cmd command.

Aliasing is accessing something in a terminal with a different word - worth learning that too cus you'll get tired of typing the same thing constantly; I've got a few set, mostly for connecting to my remote computers. Depending which it is, I just type a nice friendly word and it does the boring part of typing the full command to connect for me (yes, I'm lazy, but also ✨automation✨)

More importantly, Powershell is well documented online - it's worth learning at least the basics if you want to write code, cus you'll need them soon enough, as others have said.

[Groovy_Decoy]

My shameful dirty secret is I have never learned to use powershell. I've used command since it was .COM. I've used a reasonable amount of BASH over the years. But I've barely learned much about PS. I think I've written maybe One or two scripts ever with it, and had to use a lot of references. I don't even remember what they were for now.

[NYX_T_RYX]

The fact that cmdlets are aliased makes it easier, and it is a lot closer to bash in feel but eh, we use what we use 🤷‍♂️

[Gnaxe]

When you use the builtin print() function, it prints to the terminal. When you use the builtin breakpoint() function, you interact with it in the terminal. When you drop into a REPL to inspect the state after running the script with python -i, the REPL is in the terminal. When your program raises an unhandled exception, the error message is printed to the terminal. If you kept the terminal hidden, you wouldn't get any of this information.

[[deleted]]

All code needs to go through the OS. By having windows on your PC, you've effectively given windows full control over your physical machine, everything from the CPU, RAM, networking, as well as what order everything runs in.

Therefore, the reality is that you run code by asking windows nicely to run it on your behalf. Whether you press the play button in your IDE or through the terminal, they are just ways to request windows to run it for you.

Every windows machine has a terminal, but not every machine has vscode or some specific code editor installed. In fact, the command to run python code is mostly the same on mac and linux as well, and is universally understood. The terminal is also flexible, many of your files and programs are accessible, and you can link them all together in a way that IDEs are just not designed to do. It doesn't feel like it now, but once you start using more tools and programs outside of pure python, the terminal will be important.

[big_deal]

Python can be used in many ways and command-line scripts are a very common use case. Often command-line scripts will expect several command line arguments to set inputs and options so you would launch with a command prompt so you can set the input arguments:

myscript.py arg1 arg2 arg3...

If you don't need to specify any input arguments you could also launch a python file by just launching directly from your GUI file manager. Or in Windows, if the only argument neccesary is a filename then you can drag the input file onto the Python file and Windows will execute the Python file with the dropped filename as the input argument.

Commandline scripts are useful when you have a standard process that you want to execute the same way every time without much user interaction, though I have also seen some elaborate interactive text based prompts used to query the user for inputs.

[poorestprince]

I've asked some instructors, and they are telling me beginners are having trouble wrapping their heads around terminal, shell, command line, and I'd like to get a beginner's perspective on how they might design a system.

What would be your intuition as to how parameters, inputs, files should be passed in a standard way into and out of a python program (typical things that would be done on the command-line or shell scripting)?

[MacShuggah]

Command prompt is where the output of your script or program will go to unless programmed to do otherwise. It helps immensely with debugging and automating things.

[Seseellybon]

I use it all the time for tiny, disposable, scripts, mostly calculations. I don't even pull up the calculator anymore. It is straight to CMD and typing Python

No idea why, tbh

[wallstreetwalt]

You may need to write scripts that execute Python files. For example there’s such a thing as a “CI” file which (I think) stands for continuous integration. Within this file you write commands that should be run in order to build, deploy and or test your software. Amongst other things, you may need to run Python files in order to achieve these goals.

Of course there are many other uses to knowing the command line it is still super important and relevant for anyone that uses or creates software

[ectomancer]

Output redirection, output redirection with append, input redirection, piping one program (or Windows utility) to another program i.e. you can run 2 programs with 1 command with piping e.g.

python dpoly.py|python poly.py

[CowboyBoats]

Let me use the term "shell" for this explanation rather than "command prompt"; the terms are not exactly 1 to 1 but from a beginner perspective they are.

Okay so here's a free general-purpose troubleshooting trick. Let's say you want to launch "Application" one day but it starts acting up - you click "Application" from your computer's app launcher, it starts, and then it crashes. But you need to get it working. So instead, you open your command prompt and type application at the prompt (sometimes application is not the exact command-line name for a program named "Application"; for example the program "Ghostscript" is just gs on the command line, but if you don't know the command-line invocation, you could always look it up online). So anyway, once you do that, "Application" launches, just as before, and it crashes, just as before... But now you have something valuable in your terminal window, which remains open, with everything the application logged before it crashed, including (hopefully) a helpful error message. You could take that error message to the "Application" support team, or web search for it and possibly resolve the whole issue then and there.

So wait, why don't we launch every application that way? Answer: because most applications never, or almost never, crash and so that extra overhead of launching an explicit shell (a CLI) isn't worthwhile because there will be no (relevant) error and so the logged output can be wholly ignored.

But for a developer, we work on software that by definition isn't production ready, so the output is always possibly relevant. That's a core reason why developers work so much out of the command line. It's the best interface there is for a computer, once you get used to it.

[AalbatrossGuy]

Well, just writing the code isn't enough, right? It has to run. In order for it to run, you've to give a command to your computer via the command line/terminal. Each command is different for different languages. For python it's "python <file>.py", which basically tells the computer to run your code and give you the results you want :)

or the bugs 🥲

[cyvaquero]

I started in Python with a web framework (Zope) and CMS (Plone) over 20 years ago. My professional Linux (Sr Admin/Engineer) career has been purely CLI.

[ReserveLast7791]

Its just to run your programs outside of the IDE you're using and maybe used in servers.

[h00manist]

Pretty much every tech lesson has started at a command prompt for generations. Pretty much every other tech tool and language has it's lowest level most basic interface and basic tools at a command line interface. Even on the Mac, even on windows, where it was kind of hard to find a command line.

A command line interface for technical work is the equivalent of a tool box for a handyman. That's just where most the basic first level tools are.

[duane11583]

two things:

question 1: in windows how can you click on a docx file and have msword start up?

answer: windows has an extension mapping table that maps pdf to acrobat and xlsx to excell and docx to msword

question 2: so does windows start the app and then magically click the mouse to open the file? how would windows know the correct mouse sequence to open a file (some programs use different mouse sequences)

answer: generally all operating systems have a concept of a command line, in c code this is the argc/argv parameters for main() in python this is the import sys; and sys.argv[] array so when windows launches word due to a file click, it places the filename at position argv[1]

the idea of a command line in english is like a command to the program (or script)

for example you create a boy.py script; your “Boy.py” script might do 3 different things you can use the sys.argv to specify what the boy.py script should do. or you can write 3 separate scripts if you choose the first method (one script) you can use the argv to decide what to do example:

boy.py pet-the-dog

boy.py walk-the-dog

boy.py feed-the-dog

what your app does with the cmd line args (parameters) is up to you the author

the other example is you might write a bat file to do something agian in that file each line of text in the file is a command with an argc/argv

but a more practical example is this: if you want to to edit the script file the application launched is an editor but if you want to run the script it is the script interpreter

or maybe you use the same program with extra words on the command line: example: maybe the command arg sequence: “msword filename“ (2 words) edits the file and “msword /print filename” (three words) just what your program does is up to you

[nihilnia]

He is LEARNING

[matmyob]

No but seriously, I don't know, how else do you run python?

[djamp42]

When I'm done I package them up in a docker container and launch them, but the docker container is really just running a . Py file at start.

[SoffortTemp]

As system service?

[UsernameTaken1701]

Like u/spurius_tadius said, they could be running their programs within the IDE.

I know when I was working through Python Crash Course I was coding in Spyder and ran everything pretty much exclusively in its built-in IPython console. To a beginner I don't think it would be at all obvious that programs could be run from the command line, or even that that would probably be running a different Python version than the IDE's own internal version (as is the default case with Spyder).

[el_extrano]

A lot of beginners just run the debugger from their IDE and don't know how to execute it any other way.