comparing batch to python commands? - python

Ok i have these commands used in batch and i wanted to know the commands in python that would have a similar affect, just to be clear i dont want to just use os.system("command here") for each of them. For example in batch if you wanted a list of commands you would type help but in python you would type help() and then modules... I am not trying to use batch in a python script, i just wanna know the similarities in both languages. Like in english you say " Hello" but in french you say "Bonjour" not mix the two languages. (heres the list of commands/functions id like to know:
change the current directory
clear the screen in the console
change the prompt to something other than >>>
how to make a loop function
redirections/pipes
start an exteral program (like notepad or paint) from within a script
how to call or import another python script
how to get help with a specific module without having to type help()
#8: (in batch it would be command /?)
EDITED COMPLETELY
Thanks in Adnvance!

You can't just mechanically translate batch script to Python and hope that it works. It's a different language, with different idioms and ways of doing things, not to mention the different purpose.
I've listed some functions related to what you want below, but there's no substitute for just going and learning Python!
os.chdir
os.system("cls") is probably the simplest solution
Change sys.ps1 and sys.ps2.
Nope, there are no gotos in Python. Use for and while loops instead.
Doesn't make sense, use Python's IO instead.
subprocess.Popen
Doesn't make sense, use import or subprocess.Popen instead.
help

Most of the things you've mentioned (start, cls etc.) are not "batch commands", they're executable programs which perform certain tasks. The DOS "shell" simply executes these when it encounters them in a file. In this sense, "python" is the equivalent of a single executable (like cls).
Now that that's clear, cd (and most other OS specific tasks) are accomplished using the os module. There's no single Python statement to clear the screen - that would be wasteful. Changing the prompt of the python interpreter can be done by assigning to sys.ps1. Loops are done using while or for. Redirection doesn't happen. YOu can however use the subprocess module to run subcommands and send their outputs to files or other streams. Starting commands is done using the subprocess.Popen function. For getting help, you can either do help("command") or if you're using ipython, just say command? and hit enter.
You should really go through the tutorial rather than trying to map batch commands to Python.

The Python docs are excellent, and are the place to start. For doing shell-script like things, you'll want to check out:
http://docs.python.org/library/os.html?module-os
http://docs.python.org/library/os.path.html#module-os.path
http://docs.python.org/library/shutil.html#module-shutil
http://docs.python.org/library/subprocess.html#module-subprocess

Python is not a system shell, Python is a multi-paradigm programming language.
If you want to compare .bat with anything, compare it with sh or bash. (You can have those on various platforms too - for example, sh for windows is in the MinGW package).

I am pretty much facing the same problem as you, daniel11. As a solution, I am learning BATCH commands and their meaning. After I understand those, I am going to write a program in Python that does the same or accomplishes the same task.
Thanks to Adam V. and katrielatex for their insight and suggestions.

Related

How can I call a python function from an advanced scripting voice command in Dragon NaturallySpeaking?

How can I call a python function from an advanced scripting voice command in Dragon NaturallySpeaking?
I don't want to use a third-party application such as dragonfly or NatLink (paper).
So, one way is to compile it. You can put a bunch of functions that do different things all into the same program and pass along appropriate arguments to select the function you want, and pass the parameters along. Returning the result can be tricky, though, but I usually use the Clipboard (so copy the py output to clip and read from clip in Dragon). Multi-word params need to have spaces escaped (%20) and process it inside your py.
Something like this:
ShellExecute "path\program.exe myFunc myPar1, my%20Par%202", 6 ' 6 runs minimized
Wait 1
myVar = Clipboard
Hth,
Warning: This is not an answer. I am not a programmer. I don't know any Python and have no way of testing it.
This is just a suggestion on how to solve this problem. I don't know where else to put this. I'd put it in a comment, but it allows no screenshots. Please edit and suggest as you wish.
There is answer on SO that deals with calling Python from Excel, which is a similar concept: https://stackoverflow.com/a/3569988/2101890. I am trying to use that here but don't know how.
When using commands in another programming language, you can sometimes add them by adding a reference in the MyCommands Editor. You can reference DLLs and other "stuff". Some references to libraries appear automatically. I've installed Python and hoped to find Python in the References, but no such luck:
There is no Python entry here that I can find. You may have better luck. If you do find something, check the box and see if you can add python commands without causing an error when saving the command.
Maybe you can browse to %localappdata%\Programs\Python\Python36\ and add some of the DLLs from there and call Python commands from there. Or try getting it to work in the way described under 1.

getting bash completion options programmatically

I want a function that programmatically returns completion options from either bash or zsh. There are lots of examples of related questions on stackoverflow but no proper, generic answers anywhere. I do NOT want to know how to write a specific completer function for bash.
I've already tried implementing this by reading debian /etc/completion shell code, by echoing control-codes for tab into "bash -i", and even tried using automated subprocess interaction with python-pexpect. Every time I thought I was successful, I find some small problem that invalidates the whole solution. I'd accept a solution in any language, but ideally it would be python. Obviously the exact input output would vary depending on systems, but take a look at the example I/O below:
function("git lo") returns ["log","lol","lola"]
function("apt-get inst") returns ["apt-get install"]
function("apt-get") returns []
function("apt-get ") returns ["apt-get autoclean","apt-get autoremove", ...]
function ("./setup") returns ["./setup.py"]
If you are thinking of a solution written in shell, it would ideally be something I can execute without "source"ing. For instance bash "compgen" command looks interesting (try "compgen -F _git"), but note that "bash -c 'compgen -F _git'" does not work because the completion helper "_git" is not in scope.
This gist is my best solution so far. It meets all the requirements, works well for multiple versions of bash on multiple OS's but it requires a subprocess call and it's so complicated it's absurd. The comments includes full documentation of all the outrageous slings and arrows. I'm still hoping for something more reasonable to come along, but unless it does.. this is it!

Using Python 3 with Python 2

I have a Python 3 file. I want to use an open-source tool on the internet (nltk), but unfortunately it only supports Python 2. There is no way for me to convert it to Python 3, nor can I convert my Python 3 file to Python 2.
If the user does not give a certain argument (on argparse) then I do something in my file. If the user does give a certain argument, however, I need to use nltk.
Writing a Python 2 script that uses nltk and then executing script that in my Python 3 script
My current idea is to write a script in Python 2 that does what I want with nltk and then run that from my current Python 3 script. However, I don't actually know how to do this.
I found this code: os.system(command) and so I will modify it to be os.system("python py2.py") (where py2.py is my newly written Python 2 file).
I'm not sure if that will work.
I also don't know if that is the most efficient way to solve my problem. I cannot find any information about it on the internet.
The data transferred will probably be quite large. Currently, my test data is about 6600 lines, utf-8. Functionality is more important than how long it takes (to a certain extent) in my case.
Also, how would I pass values from my Python 2 script to my Python 3 script?
Thanks
Is there any other way to do this?
Well, if you're sure you can't convert your script to Python 2, then having one script call the other by running the Python interpreter probably is the best way. (And, this being Python, the best way is, or at least should be, the only way.)
But are you sure? Between the six module, the 3to2 tool, and __future__ statements, it may not be as hard as you think.
Anyway, if you do need to have one script call the other, you should almost never use os.system. As the docs for that function say:
The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function. See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes.
The simplest version is this:
subprocess.check_call(["python", "py2.py"])
This runs your script, waits for it to finish, and raises an exception if the script returns failure—basically, what you wanted to do with os.system, but better. (For example, it doesn't spawn an unnecessary extra shell, it takes care of error handling, etc.)
That assumes whatever other data you need to share is being shared in some implicit, external way (e.g., by accessing files with the same name). You might be better off passing data to py2.py as command-line arguments and/or stdin, passing data back as via stdout, or even opening an explicit pipe or socket to pass things over. Without knowing more about exactly what you need to do, it's hard to suggest anything, but the docs, especially the section Replacing Older Functions with the subprocess Module have lots of discussion on the options.
To give you an idea, here's a simple example: to pass one of your filename arguments to py2.py, and then get data back from py2.py to py3.py, just have py3.py do this:
py2output = subprocess.check_output(["python", "py2.py", my_args[0]])
And then in py2.py, just print whatever you want to send back.
The Anyone hear when NLTK 3.0 will be out? here in SO points out that...
There's a Python 3 branch:
https://github.com/nltk/nltk/tree/nltk-py3k
The answer is from July 2011. It could be improved since then.
I have just looked at https://github.com/nltk/nltk. There is at least the document that talks about Python 3 port related things https://github.com/nltk/nltk/blob/2and3/web/dev/python3porting.rst.
Here is a longer discussion on NLTK and Python 3 that you may be interested in.
And the Grants to Assist Kivy, NLTK in Porting to Python 3 (published 3 days ago) is directly related to the problem.

Can You Embed an TCL Script in Bash Script or Python Script That's Callable by External Programs?

I'm writing a script to extract some useful data about a series of chemical simulations I've been running.
To get this data I need (1) a C-program that calculates the density from a file type called *.pdb. I already have (1). And (2) I need to use a program called vmd to get that pdb. In order to accomplish (2) from the command line, I can submit a tcl script, as vmd has a build in tcl interpreter.
These functions -- calling the vmd to run the tcl script, then running the compiled c-program -- will be the key activities of my wrapper data extraction script.
I would like to eliminate the superfluous TCL script, reducing my count from 2 scripts (wrapper script + tcl script for vmd) down to 1. But I'm not sure quite how to do this. One potentially solution seems to be to embed my TCL script within my wrapper script, if there's a way to make such an embedded script callable from external programs.
Most of my data collection scripts so far have been in BASH, so ideally I would like to stick to a BASH script as I'm very familiar with bash scripting versus having only beginning knowledge of Python/Perl.
Here are my questions:
1. Can you embed a TCL script inside a Bash script?
2. Can you make this script callable by an external program?
e.g. in pseudocode:
#!/bin/bash
....
tclembed extract {
#tcl script
...
}
...
vmd -dispdev text -e extract.tcl >& extract_results.log #where vmd is
#an external program
3. If the answer to #2 is no, can you do this in Python, perhaps with the Minotaur library? I would consider the switch to python, if so...
http://markmail.org/message/6kogjphzqtn4ilch
4. If not, how would you suggest trying to merge these two scripts (a tcl routine and a bash script that calls it) into a single file?
5. If anybody HAS gotten external calls of this nature to work using Minotaur, can you post some explanatory code?
I've thought of one non-embedding solution which to #4, which would be to write a function in my Bash script that writes a file with the entire tcl script. That way I would have a single script, but could dump the subscript for use with external programs, later deleting it. I have a feeling this solution is kinda kludgy though I know for sure that it works, vs. embedded solutions.
There have been several Tcl-Python alloys. As Rafe Kettler's comment above sketches, the place to start is with a standard Python installation. This includes Tkinter, which builds in a full Tcl interpreter, accessible as described in the Wiki page mentioned. So, yes, it is feasible to "do this in Python".
I really don't get what this has to do with vmd, though. vmd builds in a Tcl interpreter already. While I entirely support the aim of "reduction of moving parts", so that you have, for example, one script, rather than two, coding something in Python, when vmd already exposes Tcl, doesn't seem like a step in the direction Jason R. Mick wants to go.
SOMEWHAT LATER: after an exchange of comments with Jason R. Mick, it occurred to me he might find
#!/bin/bash
echo "Here's a bit of bash-iness."
MYSCRIPT='
puts "Here I am, inside Tcl."
puts "See? I can do calculations: [expr 3 + 5]."
exit 0
'
tclsh << HERE
$MYSCRIPT
HERE
suggestive. Its output, of course, is
Here's a bit of bash-iness.
Here I am, inside Tcl.
See? I can do calculations: 8.
I wrote this in terms of tclsh, but, if I'm keeping up, Jason R. Mick will actually want to use vmd. The appropriate homologue for *vmd is something like
...
vmd -dispdev text -eofexit << HERE > output.log
$MYSCRIPT
HERE
While I can think of several other ways to meld bash and Tcl, I believe this one is most in the spirit of the original question.
I want to note, too, that, from the little I know of vmd, it would be entirely appropriate to do the same with Python in place of Tcl: vmd is equally adept with either.
Finally, both Python and Tcl are general-purpose languages, with approximately the same power as bash, so yet another direction to take this project would be to write it entirely in Tcl (or Python), rather than bash. Embedding scripts in the way illustrated above is at least as easy in Tcl (or Python) as in bash.
1. Can you embed a TCL script inside a Bash script?
Not easily. The best way is to write the script to a temporary file and pass the name of that file to tclsh (or wish if it is a Tcl/Tk program). That should be a "simple matter of programming", i.e., some awkward coding but not fundamentally hard.
2. Can you make this script callable by an external program?
I don't quite understand what you want to do here. You can put a #! line at the start of a Tcl script and mark the file executable. That works well. The best way of all to do that is this:
#!/usr/bin/env tclsh8.5
your tcl script here...
3. If the answer to #2 is no, can you do this in Python?
This wiki page mentions something called Typcl, which is reported to allow doing Tcl from inside Python. I have never tried it.
(I think questions 4 and 5 are largely irrelevant based on my answers above.)

Python - When Is It Ok to Use os.system() to issue common Linux commands

Spinning off from another thread, when is it appropriate to use os.system() to issue commands like rm -rf, cd, make, xterm, ls ?
Considering there are analog versions of the above commands (except make and xterm), I'm assuming it's safer to use these built-in python commands instead of using os.system()
Any thoughts? I'd love to hear them.
Rule of thumb: if there's a built-in Python function to achieve this functionality use this function. Why? It makes your code portable across different systems, more secure and probably faster as there will be no need to spawn an additional process.
One of the problems with system() is that it implies knowledge of the shell's syntax and language for parsing and executing your command line. This creates potential for a bug where you didn't validate input properly, and the shell might interpet something like variable substitution or determining where an argument begins or ends in a way you don't expect. Also, another OS's shell might have divergent syntax from your own, including very subtle divergence that you won't notice right away. For reasons like these I prefer to use execve() instead of system() -- you can pass argv tokens directly and not have to worry about something in the middle (mis-)parsing your input.
Another problem with system() (this also applies to using execve()) is that when you code that, you are saying, "look for this program, and pass it these args". This makes a couple of assumptions which may lead to bugs. First is that the program exists and can be found in $PATH. Maybe on some system it won't. Second, maybe on some system, or even a future version of your own OS, it will support a different set of options. In this sense, I would avoid doing this unless you are absolutely certain the system you will run on will have the program. (Like maybe you put the callee program on the system to begin with, or the way you invoke it is mandated by something like POSIX.)
Lastly... There's also a performance hit associated with looking for the right program, creating a new process, loading the program, etc. If you are doing something simple like a mv, it's much more efficient to use the system call directly.
These are just a few of the reasons to avoid system(). Surely there are more.
Darin's answer is a good start.
Beyond that, it's a matter of how portable you plan to be. If your program is only ever going to run on a reasonably "standard" and "modern" Linux then there's no reason for you to re-invent the wheel; if you tried to re-write make or xterm they'd be sending the men in the white coats for you. If it works and you don't have platform concerns, knock yourself out and simply use Python as glue!
If compatibility across unknown systems was a big deal you could try looking for libraries to do what you need done in a platform independent way. Or you need to look into a way to call on-board utilities with different names, paths and mechanisms depending on which kind of system you're on.
The only time that os.system might be appropriate is for a quick-and-dirty solution for a non-production script or some kind of testing. Otherwise, it is best to use built-in functions.
Your question seems to have two parts. You mention calling commands like "xterm", "rm -rf", and "cd".
Side Note: you cannot call 'cd' in a sub-shell. I bet that was a trick question ...
As far as other command-level things you might want to do, like "rm -rf SOMETHING", there is already a python equivalent. This answers the first part of your question. But I suspect you are really asking about the second part.
The second part of your question can be rephrased as "should I use system() or something like the subprocess module?".
I have a simple answer for you: just say NO to using "system()", except for prototyping.
It's fine for verifying that something works, or for that "quick and dirty" script, but there are just too many problems with os.system():
It forks a shell for you -- fine if you need one
It expands wild cards for you -- fine unless you don't have any
It handles redirect -- fine if you want that
It dumps output to stderr/stdout and reads from stdin by default
It tries to understand quoting, but it doesn't do very well (try 'Cmd" > "Ofile')
Related to #5, it doesn't always grok argument boundaries (i.e. arguments with spaces in them might get screwed up)
Just say no to "system()"!
I would suggest that you only use use os.system for things that there are not already equivalents for within the os module. Why make your life harder?
The os.system call is starting to be 'frowned upon' in python. The 'new' replacement would be subprocess.call or subprocess.Popen in the subprocess module. Check the docs for subprocess
The other nice thing about subprocess is you can read the stdout and stderr into variables, and process that without having to redirect to other file(s).
Like others have said above, there are modules for most things. Unless you're trying to glue together many other commands, I'd stick with the things included in the library. If you're copying files, use shutil, working with archives you've got modules like tarfile/zipfile and so on.
Good luck.

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