If the definition of the shell is:
In computing, a shell is a user interface for access to an operating
system's services. In general, operating system shells use either a
command-line interface (CLI) or graphical user interface (GUI),
depending on a computer's role and particular operation. It is named a
shell because it is the outermost layer around the operating system
kernel.
And shell scripting is:
A shell script is a computer program designed to be run by the Unix
shell, a command-line interpreter.
Could we say correctly that a python script is a shell script to, but this is not a Bash script?
Writing Python programs is not "shell scripting". There is no OS shell involved in running a Python program. Some people call Python (and other languages) a "scripting language," but that is a vague term with no clear definition. Python is a programming language, and when you write Python programs, you are programming.
Shell scripting is using shell commands, which is different than Python scripting.
Unlike Python scripts, shell scripts do not need a shebang. Your quote explains it clearly:
A shell script is a computer program designed to be run by the Unix
shell, a command-line interpreter.
It clearly defines shell scripts as they run by Unix shell. Python scripts on the other hand, are run by Python interpreter, not by the shell.
Therefore Python scripts are not shell scripts. Keep in mind that you use shell to run the Python code but shell actually forwards script content to Python interpreter, with the help of shebang.
Related
1) I am new to Python and love to learn its core. I have downloaded the python software package and discovered the python.exe application inside. I double clicked it and a balck and white window popped up.
Should I call it a python Interpreter or python Shell?
2) I am learning python online. I came across the terms python tty, python shell and python interpreter. I am satisfied by calling that screen inside the window as a tty(TeleTYpewriter) because we could use only keyboard to work inside and no mouse. But actually that screen has got some intelligence responding to our request. Is python tty an apt term for it?
3) In UNIX, shell is an user interface and command line interpreter, so does python interpreter and python shell are the same.
Python shell lets you use the Python interpreter in interactive mode, just as an OS shell, such as bash, lets you use the OS in interactive mode. You can use the Python interpreter in script mode or batch mode wherein you let the interpreter execute all lines of code in one sequence. It is comparable to writing shell scripts (or batch files in Microsoft Windows).
In your case the screenshot is of a python "shell".
You shouldn't really pay attention to this distinction because in the end everything runs through the python interpreter be it in interactive mode or not.
It is both the python shell and the python interpreter. The shell is where you write your code directly in the CLI, whereas the interpreter is the program that will interpret your code and execute it. Therefore, the interpreter is called in the shell when you write some code, it may also be called when you execute some python code directly from a file.
The customary term for the interactive Python shell is the Python REPL. Many modern interpreters enter a Read-Eval-Print-Loop when you run them interactively, and this term has stuck.
The program which interprets and executes your Python code is the Python interpreter; it can act as a shell, as described above, or run silently and just execute your Python code without any visible user interface of its own, like when you run a script of yours with
python scriptname.py
As python has two ways to code one from python command and one from python shell what is the difference between these two?
Python Shell is a command line tool that starts up the python interpreter. You can test simple programs and also write some short programs. However, in order to write a more complexed python program you need an editor. IDLE, on the other hand, has combined the above two needs and bundled them as a package. IDLE consists of Python Shell, and Text editor that supports highlights for python grammar and etc.
Is it possible to wrap the standard python interpreter inside a bash script or similar, so the interpreter is called within slurm or any other program, and this script can be used as a remote interpreter in PyCharm?
The situation is I need to call the python interpreter remotely using slurm (and not as standalone), with a command like:
srun ---mem=10G python
A simple script doesn't seem to do the job. I can use remotely the python interpreter without slurm in PyCharm, but I need to use it within slurm. I've also tried to do it within PyCharm, but I haven't managed to do so.
Thanks in advance.
I written a simple shell in python and compiled it with nuitka.
My shell as some simple commands, such as "say string", "braille string", "stop" etc.
This program uses python accessible_output package to communicate with screen reader in windows.
Ok, this works well froma a normal shell, or executing it from windows.
Now, I would like run this program from within emacs, such as normal shell in emacs.
I tried some functions, "start-process", "shell-command", but I can't write commands.
My program displays a prompt, like python interpreter, where I can put my commands.
Elisp is able to run python shells, mysql shells, but I'm unable to run my own shell.
Help!
Emacs has a number of different ways to interact with external program. From your text, I suspect you need to look at comint in the emacs manual and the elisp reference manual. Comint is the low level general shell in a buffer functionality (it is what shell mode uses).
Reading between the lines of your post, I would also suggest you have a look at emacspeak. and speechd.el, both of which are both packages which add speech to emacs. Speechd.el is bare bones and uses speech-dispatcher while emacspeak is very feature rich. The emacspeak package uses a Tcl script which communicates with hardware or software speech servers. It also has a mac version written in python which communicates with the OSX accessiblity (voiceOver) subsystem. Looking at how these packages work will likely give you good examples on how to make yours do what you want.
Take a look at how it's done in the nodejs-repl https://github.com/abicky/nodejs-repl.el/blob/develop/nodejs-repl.el (see line 308)
In python-mode.el, the part in question reads
(with-current-buffer
(apply #'make-comint-in-buffer executable py-buffer-name executable nil (split-string-and-unquote args))
See docstring of make-comint-in-buffer for details.
What about just launching your script from inside an emacs shell buffer?
M-x shell RET /path/to/my/script RET
I'd like to call a separate non-child python program from a python script and have it run externally in a new shell instance. The original python script doesn't need to be aware of the instance it launches, it shouldn't block when the launched process is running and shouldn't care if it dies. This is what I have tried which returns no error but seems to do nothing...
import subprocess
python_path = '/usr/bin/python'
args = [python_path, '&']
p = subprocess.Popen(args, shell=True)
What should I be doing differently
EDIT
The reason for doing this is I have an application with a built in version of python, I have written some python tools that should be run separately alongside this application but there is no assurance that the user will have python installed on their system outside the application with the builtin version I'm using. Because of this I can get the python binary path from the built in version programatically and I'd like to launch an external version of the built in python. This eliminates the need for the user to install python themselves. So in essence I need a simple way to call an external python script using my current running version of python programatically.
I don't need to catch any output into the original program, in fact once launched I'd like it to have nothing to do with the original program
EDIT 2
So it seems that my original question was very unclear so here are more details, I think I was trying to over simplify the question:
I'm running OSX but the code should also work on windows machines.
The main application that has a built in version of CPython is a compiled c++ application that ships with a python framework that it uses at runtime. You can launch the embedded version of this version of python by doing this in a Terminal window on OSX
/my_main_app/Contents/Frameworks/Python.framework/Versions/2.7/bin/python
From my main application I'd like to be able to run a command in the version of python embedded in the main app that launches an external copy of a python script using the above python version just like I would if I did the following command in a Terminal window. The new launched orphan process should have its own Terminal window so the user can interact with it.
/my_main_app/Contents/Frameworks/Python.framework/Versions/2.7/bin/python my_python_script
I would like the child python instance not to block the main application and I'd like it to have its own terminal window so the user can interact with it. The main application doesn't need to be aware of the child once its launched in any way. The only reason I would do this is to automate launching an external application using a Terminal for the user
If you're trying to launch a new terminal window to run a new Python in (which isn't what your question asks for, but from a comment it sounds like it's what you actually want):
You can't. At least not in a general-purpose, cross-platform way.
Python is just a command-line program that runs with whatever stdin/stdout/stderr it's given. If those happen to be from a terminal, then it's running in a terminal. It doesn't know anything about the terminal beyond that.
If you need to do this for some specific platform and some specific terminal program—e.g., Terminal.app on OS X, iTerm on OS X, the "DOS prompt" on Windows, gnome-terminal on any X11 system, etc.—that's generally doable, but the way to do it is by launching or scripting the terminal program and telling it to open a new window and run Python in that window. And, needless to say, they all have completely different ways of doing that.
And even then, it's not going to be possible in all cases. For example, if you ssh in to a remote machine and run Python on that machine, there is no way it can reach back to your machine and open a new terminal window.
On most platforms that have multiple possible terminals, you can write some heuristic code that figures out which terminal you're currently running under by just walking os.getppid() until you find something that looks like a terminal you know how to deal with (and if you get to init/launchd/etc. without finding one, then you weren't running in a terminal).
The problem is that you're running Python with the argument &. Python has no idea what to do with that. It's like typing this at the shell:
/usr/bin/python '&'
In fact, if you pay attention, you're almost certainly getting something like this through your stderr:
python: can't open file '&': [Errno 2] No such file or directory
… which is exactly what you'd get from doing the equivalent at the shell.
What you presumably wanted was the equivalent of this shell command:
/usr/bin/python &
But the & there isn't an argument at all, it's part of sh syntax. The subprocess module doesn't know anything about sh syntax, and you're telling it not to use a shell, so there's nobody to interpret that &.
You could tell subprocess to use a shell, so it can do this for you:
cmdline = '{} &'.format(python_path)
p = subprocess.Popen(cmdline, shell=True)
But really, there's no good reason to. Just opening a subprocess and not calling communicate or wait on it already effectively "puts it in the background", just like & does on the shell. So:
args = [python_path]
p = subprocess.Popen(args)
This will start a new Python interpreter that sits there running in the background, trying to use the same stdin/stdout/stderr as your parent. I'm not sure why you want that, but it's the same thing that using & in the shell would have done.
Actually I think there might be a solution to your problem, I found a useful solution at another question here.
This way subprocess.popen starts a new python shell instance and runs the second script from there. It worked perfectly for me on Windows 10.
You can try using screen command
with this command a new shell instance created and the current instance runs in the background.
# screen; python script1.py
After running above command, a new shell prompt will be seen where we can run another script and script1.py will be running in the background.
Hope it helps.