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How do I execute a program from Python? os.system fails due to spaces in path

I have a Python script that needs to execute an external program, but for some reason fails.

If I have the following script:

import os;
os.system("C:\\Temp\\a b c\\Notepad.exe");
raw_input();

Then it fails with the following error:

'C:\Temp\a' is not recognized as an internal or external command, operable program or batch file.

If I escape the program with quotes:

import os;
os.system('"C:\\Temp\\a b c\\Notepad.exe"');
raw_input();

Then it works. However, if I add a parameter, it stops working again:

import os;
os.system('"C:\\Temp\\a b c\\Notepad.exe" "C:\\test.txt"');
raw_input();

What is the right way to execute a program and wait for it to complete? I do not need to read output from it, as it is a visual program that does a job and then just exits, but I need to wait for it to complete.

Also note, moving the program to a non-spaced path is not an option either.

This does not work either:

import os;
os.system("'C:\\Temp\\a b c\\Notepad.exe'");
raw_input();

Note the swapped single/double quotes.

With or without a parameter to Notepad here, it fails with the error message

The filename, directory name, or volume label syntax is incorrect.


D
Daniel Rikowski

subprocess.call will avoid problems with having to deal with quoting conventions of various shells. It accepts a list, rather than a string, so arguments are more easily delimited. i.e.

import subprocess
subprocess.call(['C:\\Temp\\a b c\\Notepad.exe', 'C:\\test.txt'])

It is much simpler to use raw string in windows: r"C:\Temp\a b c\Notepad.exe"
Yes, the os.exec* functions will replace the current process, so your python process won't continue. They're used more on unix where the general method for a shell to launch a command is to fork() and then exec() in the child.
The windows method for this is the os.spawn family, which could be used instead. subprocess is more portable though, and offers more flexibility in controlling the process (capturing input/output etc), so is preferred.
@PierreBdr: There is a case where rawstrings won't work: where you need a trailing slash. eg r'c:\foo\bar\'. Actually, its probably better to use forward slashes instead. These are accepted throughout the windows API (though not always by some shell commands (eg copy))
For python >= 3.5 subprocess.call should be replaced by subprocess.run docs.python.org/3/library/subprocess.html#older-high-level-api
P
Peter Mortensen

Here's a different way of doing it.

If you're using Windows the following acts like double-clicking the file in Explorer, or giving the file name as an argument to the DOS "start" command: the file is opened with whatever application (if any) its extension is associated with.

filepath = 'textfile.txt'
import os
os.startfile(filepath)

Example:

import os
os.startfile('textfile.txt')

This will open textfile.txt with Notepad if Notepad is associated with .txt files.


Is there an equivalent function for *nix systems?
@Romeno: you could try: webbrowser.open("textfile.txt") it should open a text editor. See also "start the second program wholly on its own, as though I just 'double-clicked on it'."
P
PyGuy

The outermost quotes are consumed by Python itself, and the Windows shell doesn't see it. As mentioned above, Windows only understands double-quotes. Python will convert forward-slashed to backslashes on Windows, so you can use

os.system('"C://Temp/a b c/Notepad.exe"')

The ' is consumed by Python, which then passes "C://Temp/a b c/Notepad.exe" (as a Windows path, no double-backslashes needed) to CMD.EXE


This seems the best in a scenario like os.system('curl URL > file') where I want to see cURL's progress meter refresh for really big files.
If the first letter after a backslash has special meaning (i.e. \t, \n, etc.) then that particular backslash must be doubled. Being a Windows path has nothing to do with it.
Note that if you use os.system() on Windows the cmd window will open and remain open until you close the process that it started. IMHO it's better to use os.startfile().
Don't forget import os
D
David Ferenczy Rogožan

At least in Windows 7 and Python 3.1, os.system in Windows wants the command line double-quoted if there are spaces in path to the command. For example:

  TheCommand = '\"\"C:\\Temp\\a b c\\Notepad.exe\"\"'
  os.system(TheCommand)

A real-world example that was stumping me was cloning a drive in VirtualBox. The subprocess.call solution above didn't work because of some access rights issue, but when I double-quoted the command, os.system became happy:

  TheCommand = '\"\"C:\\Program Files\\Sun\\VirtualBox\\VBoxManage.exe\" ' \
                 + ' clonehd \"' + OrigFile + '\" \"' + NewFile + '\"\"'
  os.system(TheCommand)

That was it! I'd go for subprocess, but sometimes os.system and os.popen(...).read() are just faster to type. BTW, you don't need to escape double quotes inside single, i.e. '""C:\\Temp\\a b c\\Notepad.exe""' will do.
g
gbonetti

For python >= 3.5 subprocess.run should be used in place of subprocess.call

https://docs.python.org/3/library/subprocess.html#older-high-level-api

import subprocess
subprocess.run(['notepad.exe', 'test.txt'])

s
sarnold
import win32api # if active state python is installed or install pywin32 package seperately

try: win32api.WinExec('NOTEPAD.exe') # Works seamlessly
except: pass

and it seems no quoting is needed with this method, eg win32api.WinExec('pythonw.exe d:\web2py\web2py.py -K welcome') starts the web2py scheduler in the background.
@rahul and does it except arguments for the executable? So if you want Notepad to open a file or is that seperate?
M
Matthew Scharley

I suspect it's the same problem as when you use shortcuts in Windows... Try this:

import os;
os.system("\"C:\\Temp\\a b c\\Notepad.exe\" C:\\test.txt");

sorry, that does not work either, edited question to reflect this.
I think windows only uses ", rather than ' for quoting. This will probably work if you change this. However you'll still run into problems with if you have embedded quotes etc.
I thought it took both, but you're probably right. I know it works (in the shell atleast) with double quotes.
+1 this is the best one, windows XP, 2007 home edition worked nicely
W
WestAce

For Python 3.7, use subprocess.call. Use raw string to simplify the Windows paths:

import subprocess
subprocess.call([r'C:\Temp\Example\Notepad.exe', 'C:\test.txt'])

B
Benyamin Jafari

Suppose we want to run your Django web server (in Linux) that there is space between your path (path='/home/<you>/<first-path-section> <second-path-section>'), so do the following:

import subprocess

args = ['{}/manage.py'.format('/home/<you>/<first-path-section> <second-path-section>'), 'runserver']
res = subprocess.Popen(args, stdout=subprocess.PIPE)
output, error_ = res.communicate()

if not error_:
    print(output)
else:
    print(error_)

[Note]:

Do not forget accessing permission: chmod 755 -R <'yor path'>

manage.py is exceutable: chmod +x manage.py


T
Thomas Weller

No need for sub-process, It can be simply achieved by

GitPath="C:\\Program Files\\Git\\git-bash.exe"# Application File Path in mycase its GITBASH
os.startfile(GitPath)