I want to use metaflac (https://linux.die.net/man/1/metaflac) command from within a python script.
from subprocess import run
flac_files = "/home/fricadelle/Artist - Album (2008)/*.flac"
run(['metaflac', '--add-replay-gain', flac_files])
I get
The FLAC file could not be opened. Most likely the file does not exist
or is not readable.
if I add shell = True to the run function I'd get:
ERROR: you must specify at least one FLAC file;
metaflac cannot be used as a pipe
So what do I do wrong? Thanks!
PS: of course the command works fine in a shell:
metaflac --add-replay-gain /home/fricadelle/Artist\ -\ Album \(2008\)/*.flac
Unless you specify shell=True (and as a first approximation, you should never specify shell=True), the arguments you provide are passed as is, with no shell expansions, word-splitting or dequoting. So the filename you pass as an argument is precisely /home/fricadelle/Artist - Album (2008)/*.flac, which is not the name of any file. (That's why you don't need to add backslashes before the spaces and parentheses. If you specified shell=True -- and I repeat, you really should avoid that -- then you would need to include backslashes so that the shell doesn't split the name into several different words.)
When you type
flac_files = "/home/fricadelle/Artist - Album (2008)/*.flac unquoted in a shell, the shell will try to expand that to a list of all the files whose names match then pattern, and will then pass that list as separate arguments. Since subprocess.run doesn't do this, you will have to do it yourself, which you would normally do with glob.glob. For example,
from subprocess import run
from glob import glob
flac_files = "/home/fricadelle/Artist - Album (2008)/*.flac"
run(['metaflac', '--add-replay-gain'] + glob(flac_files))
Note: unlike the shell, glob.glob will return an empty list if the pattern matches no files. You really should check for this error rather than invoke metaflac with no filename options.
See the answer here for a better explanation.
Globbing doesn't work the way you're expecting it to here, you need to specify shell=True, but then you'll need to drop the list.
run('metaflac --add-replay-gain ' + flac_files, shell=True)
Should do the trick.
Related
I am trying to read from a file which has contents like this:
#\5\5\5
...
#\5\5\10
This file content is then fed into subprocess module of python like this:
for lines in file.readlines():
print(lines)
cmd = ls
p = subprocess.run([cmd, lines])
The output turns into something like this:
CompletedProcess(args=['ls', "'#5\\5\\5'\n"], returncode=1)
I don't understand why the contents of the file is appended with a double quote and another backward slash is getting appended.
The real problem here isn't Python or the subprocess module. The problem the use of subprocess to invoke shell commands, and then trying to parse the results. In this case, it looks like the command is ls, and the plan appears to be to read some filesystem paths from a text file (each path on a separate line), and list the files at that location on the filesystem.
Using subprocess to invoke ls is really, really, really not the way to accomplish that in Python. This is basically an attempt to use Python like a shell script (this use of ls would still be problematic, but that's a different discussion).
If a shell script is the right tool for the job, then write a shell script. If you want to use Python, then use one of the API's that it provides for interacting with the OS and the filesystem. There is no need to bring in external programs to achieve this.
import os
with open("list_of_paths.txt", "r") as fin:
for line in fin.readlines():
w = os.listdir(line.strip())
print(w)
Note the use of .strip(), this is a string method that will remove invisible characters like spaces and newlines from the ends of the input.
The listdir method provided by the os module will return a list of the files in a directory. Other options are os.scandir, os.walk, and the pathlib module.
But please do not use subprocess. 95% of the time, when someone thinks "should I use Python's subprocess module for this?" the ansewr is "NO".
It is because \ with a relevant character or digit becomes something else other than the string. For example, \n is not just \ and n but it means next line. If you really want a \n, then you would add another backslash to it (\\n). Likewise \5 means something else. here is what I found when i ran \5:
and hence the \\ being added, if I am not wrong
I am trying to execute rm command from python in linux as follows
remove_command = [find_executable(
"rm"), "-rf", "dist/", "python_skelton.egg-info", "build/", "other/*_generated.py"]
print('Removing build, dist, python_skelton.egg-
if subprocess.call(remove_command) != 0:
sys.exit(-1)
The directories gets removed successfully but the regex pattern other/*_generated.py
does not remove the relevant _generated.py files.
How shall I remove those files using regex from python script?
The reason this doesn't work the way you intend it to, is that your pattern is not expanded, but interpreted as the litteral file name "other/*_generated.py". This happens because you are relying on so-called glob pattern expansion.
The glob pattern is typically expanded by the shell, but since you are calling the rm command without using the shell, you will not get this "automatically" done. I can see two obvious ways to handle this.
Expand the glob before calling the subprocess
This can be done, using the Python standard library glob implementation:
import glob
remove_command = [find_executable("rm"), "-rf", "dist/", "python_skelton.egg-info",
"build/"] + glob.glob("other/*_generated.py")
subprocess.call(remove_command)
Use the shell to expand the glob
To do this, you need to pass shell=True to the subprocess.call. And, as always, when using the shell, we should pass the command as a single string and not a list:
remove_command = [find_executable("rm"), "-rf", "dist/", "python_skelton.egg-info",
"build/", "other/*_generated.py"]
remove_command_string = " ".join(remove_command) # generate a string from list
subprocess.call(remove_command_string, shell=True)
Both of these approaches will work. Note that if you allow user input, you should avoid using shell=True though, as it is a security hole, that can be used to execute arbitrary commands. But, in the current use case, it seems to not be the case.
the string that contains a file looks like this in the console:
>>> target_file
'src//data//annual_filings//ABB Ltd//ABB_ar_2015.pdf'
I got the target_file from a call to os.walk
The goal is to build a command to run in subprocess.call
Something like:
from subprocess import call
cmd_ = r'qpdf-7.0.0/bin/qpdf --password=%s --decrypt %s %s' %('', target_file, target_file)
call([cmd_])
I tried different variations, setting shell to either True or False.
Replacing the // with /,\ etc.
The issue seems to be with the space in the folder (I can not change the folder name).
The python code needs to run on Windows
you have to define cmd_ as a list of arguments not a list with a sole string in it, or subprocess interprets the string as the command (doesn't even try to split the args):
cmd_ = ['qpdf-7.0.0/bin/qpdf','--password=%s'%'','--decrypt',target_file, target_file]
call(cmd_)
and leave the quoting to subprocess
As a side note, no need to double the slashes. It works, but that's unnecessary.
First of all, I am new to programming.
To run python code in an external shell window, I followed the instructions given on this page
link
My problem is that if I save the python file in any path that contains a folder name with a space, it gives me this error:
C:\Python34\python.exe: can't open file 'C:\Program': [Errno 2] No such file or directory
Does not work:
C:\Program Files\Python Code
Works:
C:\ProgramFiles\PythonCode
could someone help me fix the problem???
Here is the code:
import sublime
import sublime_plugin
import subprocess
class PythonRunCommand(sublime_plugin.WindowCommand):
def run(self):
command = 'cmd /k "C:\Python34\python.exe" %s' % sublime.active_window().active_view().file_name()
subprocess.Popen(command)
subprocess methods accept a string or a list. Passing as a string is the lazy way: just copy/paste your command line and it works. That is for hardcoded commands, but things get complicated when you introduce parameters known at run-time only, which may contain spaces, etc...
Passing a list is better because you don't need to compose your command and escape spaces by yourself. Pass the parameters as a list so it's done automatically and better that you could do:
command = ['cmd','/k',r"C:\Python34\python.exe",sublime.active_window().active_view().file_name()]
And always use raw strings (r prefix) when passing literal windows paths or you may have some surprises with escape sequences meaning something (linefeed, tab, unicode...)
In this particular case, if file associations are properly set, you only need to pass the python script without any other command prefix:
command = [sublime.active_window().active_view().file_name()]
(you'll need shell=True added to the subprocess command but it's worth it because it avoids to hardcode python path, and makes your plugin portable)
I'm trying to make a python script that search words in files.
If I pass txt it will only look in files with .txt extension, but I want to pass * as argument to search in every files.
if sys.argv[4] == "*"
Don't work and if I try
print sys.argv[4]
It print the name of the script
find.py
But not the same way as
print sys.argv[0]
As it will return
./find.py
So, someone already had this problem and, of course, solved it ?
Your shell attaches meaning to * as well. You need to escape it when calling your script to prevent the shell from expanding it:
python find.py \*
sys.argv[0] is the exact name passed used to run the script. That can be a relative path (./find.py, ../bin/find.py) or an absolute path, depending on how it was invoked. Use os.path.abspath() to normalize it.