How can i get the current directory to which I am in? like the use of
os.getcwd()
First, I presume you're not asking about a particular subprocess that exists simply to tell you the current working directory and do nothing else (Apducer's answer). If that were the case you could simply as os.getcwd() and forget the subprocess. You clearly already know that. So you must be dealing with some other (arbitrary?) subprocess.
Second, I presume you understand, via dr1fter's answer, that you have control over the working directory in which the subprocess starts. I suspect that's not enough for you.
Rather, I suspect you're thinking that the subprocess might, according to its own internal logic, have changed its working directory sometime since its launch, that you can't predict where it has ended up, and you want to be able to send some sort of signal to the subprocess at an arbitrary time, to interrogate it about where it's currently working. In general, this is only possible if the process has been specifically programmed with the logic that receives such a signal (through whatever route) and issues such a response. I think that's what SuperStew meant by the comment, "isn't that going to depend on the subprocess?"
I say "in general" because there are platform-specific approaches. For example, see:
windows batch command to determine working directory of a process
How do I print the current working directory of another user in linux?
by default, subprocesses you spawn inherit your PWD. you can however, specify the cwd argument to the subprocess.Popen c'tor to set a different initial PWD.
Unix (Linux, MacOS):
import subprocess
arguments = ['pwd']
directory = subprocess.check_output(arguments)
Windows:
import subprocess
arguments = ['cd']
directory = subprocess.check_output(arguments)
If you want to run in both types of OS, you'll have to check the machine OS:
import os
import subprocess
if os.name == 'nt': # Windows
arguments = ['cd']
else: # other (unix)
arguments = ['pwd']
directory = subprocess.check_output(arguments)
I need to be able to open a document using its default application in Windows and Mac OS. Basically, I want to do the same thing that happens when you double-click on the document icon in Explorer or Finder. What is the best way to do this in Python?
Use the subprocess module available on Python 2.4+, not os.system(), so you don't have to deal with shell escaping.
import subprocess, os, platform
if platform.system() == 'Darwin': # macOS
subprocess.call(('open', filepath))
elif platform.system() == 'Windows': # Windows
os.startfile(filepath)
else: # linux variants
subprocess.call(('xdg-open', filepath))
The double parentheses are because subprocess.call() wants a sequence as its first argument, so we're using a tuple here. On Linux systems with Gnome there is also a gnome-open command that does the same thing, but xdg-open is the Free Desktop Foundation standard and works across Linux desktop environments.
open and start are command-interpreter things for Mac OS/X and Windows respectively, to do this.
To call them from Python, you can either use subprocess module or os.system().
Here are considerations on which package to use:
You can call them via os.system, which works, but...
Escaping: os.system only works with filenames that don't have any spaces or other shell metacharacters in the pathname (e.g. A:\abc\def\a.txt), or else these need to be escaped. There is shlex.quote for Unix-like systems, but nothing really standard for Windows. Maybe see also python, windows : parsing command lines with shlex
MacOS/X: os.system("open " + shlex.quote(filename))
Windows: os.system("start " + filename) where properly speaking filename should be escaped, too.
You can also call them via subprocess module, but...
For Python 2.7 and newer, simply use
subprocess.check_call(['open', filename])
In Python 3.5+ you can equivalently use the slightly more complex but also somewhat more versatile
subprocess.run(['open', filename], check=True)
If you need to be compatible all the way back to Python 2.4, you can use subprocess.call() and implement your own error checking:
try:
retcode = subprocess.call("open " + filename, shell=True)
if retcode < 0:
print >>sys.stderr, "Child was terminated by signal", -retcode
else:
print >>sys.stderr, "Child returned", retcode
except OSError, e:
print >>sys.stderr, "Execution failed:", e
Now, what are the advantages of using subprocess?
Security: In theory, this is more secure, but in fact we're needing to execute a command line one way or the other; in either environment, we need the environment and services to interpret, get paths, and so forth. In neither case are we executing arbitrary text, so it doesn't have an inherent "but you can type 'filename ; rm -rf /'" problem, and if the file name can be corrupted, using subprocess.call gives us little additional protection.
Error handling: It doesn't actually give us any more error detection, we're still depending on the retcode in either case; but the behavior to explicitly raise an exception in the case of an error will certainly help you notice if there is a failure (though in some scenarios, a traceback might not at all be more helpful than simply ignoring the error).
Spawns a (non-blocking) subprocess: We don't need to wait for the child process, since we're by problem statement starting a separate process.
To the objection "But subprocess is preferred." However, os.system() is not deprecated, and it's in some sense the simplest tool for this particular job. Conclusion: using os.system() is therefore also a correct answer.
A marked disadvantage is that the Windows start command requires you to pass in shell=True which negates most of the benefits of using subprocess.
I prefer:
os.startfile(path, 'open')
Note that this module supports filenames that have spaces in their folders and files e.g.
A:\abc\folder with spaces\file with-spaces.txt
(python docs) 'open' does not have to be added (it is the default). The docs specifically mention that this is like double-clicking on a file's icon in Windows Explorer.
This solution is windows only.
Just for completeness (it wasn't in the question), xdg-open will do the same on Linux.
import os
import subprocess
def click_on_file(filename):
'''Open document with default application in Python.'''
try:
os.startfile(filename)
except AttributeError:
subprocess.call(['open', filename])
If you have to use an heuristic method, you may consider webbrowser.
It's standard library and despite of its name it would also try to open files:
Note that on some platforms, trying to open a filename using this
function, may work and start the operating system’s associated
program. However, this is neither supported nor portable.
(Reference)
I tried this code and it worked fine in Windows 7 and Ubuntu Natty:
import webbrowser
webbrowser.open("path_to_file")
This code also works fine in Windows XP Professional, using Internet Explorer 8.
If you want to go the subprocess.call() way, it should look like this on Windows:
import subprocess
subprocess.call(('cmd', '/C', 'start', '', FILE_NAME))
You can't just use:
subprocess.call(('start', FILE_NAME))
because start is not an executable but a command of the cmd.exe program. This works:
subprocess.call(('cmd', '/C', 'start', FILE_NAME))
but only if there are no spaces in the FILE_NAME.
While subprocess.call method enquotes the parameters properly, the start command has a rather strange syntax, where:
start notes.txt
does something else than:
start "notes.txt"
The first quoted string should set the title of the window. To make it work with spaces, we have to do:
start "" "my notes.txt"
which is what the code on top does.
Start does not support long path names and white spaces. You have to convert it to 8.3 compatible paths.
import subprocess
import win32api
filename = "C:\\Documents and Settings\\user\\Desktop\file.avi"
filename_short = win32api.GetShortPathName(filename)
subprocess.Popen('start ' + filename_short, shell=True )
The file has to exist in order to work with the API call.
os.startfile(path, 'open') under Windows is good because when spaces exist in the directory, os.system('start', path_name) can't open the app correctly and when the i18n exist in the directory, os.system needs to change the unicode to the codec of the console in Windows.
I am pretty late to the lot, but here is a solution using the windows api. This always opens the associated application.
import ctypes
shell32 = ctypes.windll.shell32
file = 'somedocument.doc'
shell32.ShellExecuteA(0,"open",file,0,0,5)
A lot of magic constants. The first zero is the hwnd of the current program. Can be zero. The other two zeros are optional parameters (parameters and directory). 5 == SW_SHOW, it specifies how to execute the app.
Read the
ShellExecute API docs for more info.
Here is the answer from Nick, adjusted slightly for WSL:
import os
import sys
import logging
import subprocess
def get_platform():
if sys.platform == 'linux':
try:
proc_version = open('/proc/version').read()
if 'Microsoft' in proc_version:
return 'wsl'
except:
pass
return sys.platform
def open_with_default_app(filename):
platform = get_platform()
if platform == 'darwin':
subprocess.call(('open', filename))
elif platform in ['win64', 'win32']:
os.startfile(filename.replace('/','\\'))
elif platform == 'wsl':
subprocess.call('cmd.exe /C start'.split() + [filename])
else: # linux variants
subprocess.call(('xdg-open', filename))
If you want to specify the app to open the file with on Mac OS X, use this:
os.system("open -a [app name] [file name]")
On windows 8.1, below have worked while other given ways with subprocess.call fails with path has spaces in it.
subprocess.call('cmd /c start "" "any file path with spaces"')
By utilizing this and other's answers before, here's an inline code which works on multiple platforms.
import sys, os, subprocess
subprocess.call(('cmd /c start "" "'+ filepath +'"') if os.name is 'nt' else ('open' if sys.platform.startswith('darwin') else 'xdg-open', filepath))
On mac os you can call open:
import os
os.open("open myfile.txt")
This would open the file with TextEdit, or whatever app is set as default for this filetype.
I think you might want to open file in editor.
For Windows
subprocess.Popen(["notepad", filename])
For Linux
subprocess.Popen(["text-editor", filename])
I built a small library combining the best answers here for cross-platform support:
$ pip install universal-startfile
then launch a file or URL:
from startfile import startfile
startfile("~/Downloads/example.png")
startfile("http://example.com")
I was getting an error when calling my open file() function. I was following along with a guide but the guide was written in windows while I'm on Linux. So the os.statrfile method wasn't working for me. I was able to alleviate this problem by doing the following:
Import libraries
import sys, os, subprocess
import tkinter
import tkinter.filedioalog as fd
import tkinter.messagebox as mb
After the lib imports I then called the subprocess method for opening a file in unix based OS which is "xdg-open" and the file that will be opened.
def open_file():
file = fd.askopenfilename(title='Choose a file of any type', filetypes=[('All files', "*.*")])
subprocess.call(['xdg-open', file])
I have a .pythonrc in my path, which gets loaded when I run python:
python
Loading pythonrc
>>>
The problem is that my .pythonrc is not loaded when I execute files:
python -i script.py
>>>
It would be very handy to have tab completion (and a few other things) when I load things interactively.
From the Python documentation for -i:
When a script is passed as first argument or the -c option is used, enter interactive mode after executing the script or the command, even when sys.stdin does not appear to be a terminal. The PYTHONSTARTUP file is not read.
I believe this is done so that scripts run predictably for all users, and do not depend on anything in a user's particular PYTHONSTARTUP file.
As Greg has noted, there is a very good reason why -i behaves the way it does. However, I do find it pretty useful to be able to have my PYTHONSTARTUP loaded when I want an interactive session. So, here's the code I use when I want to be able to have PYTHONSTARTUP active in a script run with -i.
if __name__ == '__main__':
#do normal stuff
#and at the end of the file:
import sys
if sys.flags.interactive==1:
import os
myPythonPath = os.environ['PYTHONSTARTUP'].split(os.sep)
sys.path.append(os.sep.join(myPythonPath[:-1]))
pythonrcName = ''.join(myPythonPath[-1].split('.')[:-1]) #the filename minus the trailing extension, if the extension exists
pythonrc = __import__(pythonrcName)
for attr in dir(pythonrc):
__builtins__.__dict__[attr] = getattr(pythonrc, attr)
sys.path.remove(os.sep.join(myPythonPath[:-1]))
del sys, os, pythonrc
Note that this is fairly hacky and I never do this without ensuring that my pythonrc isn't accidentally clobbering variables and builtins.
Apparently the user module provides this, but has been removed in Python 3.0. It is a bit of a security hole, depending what's in your pythonrc...
In addition to Chinmay Kanchi and Greg Hewgill's answers, I'd like to add that IPython and BPython work fine in this case. Perhaps it's time for you to switch? :)
I am creating a Python script where it does a bunch of tasks and one of those tasks is to launch and open an instance of Excel. What is the ideal way of accomplishing that in my script?
While the Popen answers are reasonable for the general case, I would recommend win32api for this specific case, if you want to do something useful with it:
It goes something like this:
from win32com.client import Dispatch
xl = Dispatch('Excel.Application')
wb = xl.Workbooks.Open('C:\\Documents and Settings\\GradeBook.xls')
xl.Visible = True # optional: if you want to see the spreadsheet
Taken from a mailing list post but there are plenty of examples around.
or
os.system("start excel.exe <path/to/file>")
(presuming it's in the path, and you're on windows)
and also on Windows, just start <filename> works, too - if it's an associated extension already (as xls would be)
The subprocess module intends to replace several other, older modules and functions, such as:
os.system
os.spawn*
os.popen*
popen2.*
commands.*
.
import subprocess
process_one = subprocess.Popen(['gqview', '/home/toto/my_images'])
print process_one.pid
I like popen2 for the ability to monitor the process.
excelProcess = popen2.Popen4("start excel %s" % (excelFile))
status = excelProcess.wait()
https://docs.python.org/2/library/popen2.html
EDIT: be aware that calling wait() will block until the process returns. Depending on your script, this may not be your desired behavior.
As others have stated, I would suggest os.system. In case anyone is looking for a Mac-compatible solution, here is an example:
import os
os.system("open /Applications/Safari.app")
os.system("open file.xls")
I like os.startfile("path to file") as it opens the file as if you've double clicked to open.
I found that with os.system("start excel filename") it opened it like a file opened from the web and you had to enable editing.
I would like to use Python 2.6's version of subprocess, because it allows the Popen.terminate() function, but I'm stuck with Python 2.5. Is there some reasonably clean way to use the newer version of the module in my 2.5 code? Some sort of from __future__ import subprocess_module?
I know this question has already been answered, but for what it's worth, I've used the subprocess.py that ships with Python 2.6 in Python 2.3 and it's worked fine. If you read the comments at the top of the file it says:
# This module should remain compatible with Python 2.2, see PEP 291.
There isn't really a great way to do it. subprocess is implemented in python (as opposed to C) so you could conceivably copy the module somewhere and use it (hoping of course that it doesn't use any 2.6 goodness).
On the other hand you could simply implement what subprocess claims to do and write a function that sends SIGTERM on *nix and calls TerminateProcess on Windows. The following implementation has been tested on linux and in a Win XP vm, you'll need the python Windows extensions:
import sys
def terminate(process):
"""
Kills a process, useful on 2.5 where subprocess.Popens don't have a
terminate method.
Used here because we're stuck on 2.5 and don't have Popen.terminate
goodness.
"""
def terminate_win(process):
import win32process
return win32process.TerminateProcess(process._handle, -1)
def terminate_nix(process):
import os
import signal
return os.kill(process.pid, signal.SIGTERM)
terminate_default = terminate_nix
handlers = {
"win32": terminate_win,
"linux2": terminate_nix
}
return handlers.get(sys.platform, terminate_default)(process)
That way you only have to maintain the terminate code rather than the entire module.
While this doesn't directly answer your question, it may be worth knowing.
Imports from __future__ actually only change compiler options, so while it can turn with into a statement or make string literals produce unicodes instead of strs, it can't change the capabilities and features of modules in the Python standard library.
I followed Kamil Kisiel suggestion regarding using python 2.6 subprocess.py in python 2.5 and it worked perfectly. To make it easier, I created a distutils package that you can easy_install and/or include in buildout.
To use subprocess from python 2.6 in python 2.5 project:
easy_install taras.python26
in your code
from taras.python26 import subprocess
in buildout
[buildout]
parts = subprocess26
[subprocess26]
recipe = zc.recipe.egg
eggs = taras.python26
Here are some ways to end processes on Windows, taken directly from
http://code.activestate.com/recipes/347462/
# Create a process that won't end on its own
import subprocess
process = subprocess.Popen(['python.exe', '-c', 'while 1: pass'])
# Kill the process using pywin32
import win32api
win32api.TerminateProcess(int(process._handle), -1)
# Kill the process using ctypes
import ctypes
ctypes.windll.kernel32.TerminateProcess(int(process._handle), -1)
# Kill the proces using pywin32 and pid
import win32api
PROCESS_TERMINATE = 1
handle = win32api.OpenProcess(PROCESS_TERMINATE, False, process.pid)
win32api.TerminateProcess(handle, -1)
win32api.CloseHandle(handle)
# Kill the proces using ctypes and pid
import ctypes
PROCESS_TERMINATE = 1
handle = ctypes.windll.kernel32.OpenProcess(PROCESS_TERMINATE, False, process.pid)
ctypes.windll.kernel32.TerminateProcess(handle, -1)
ctypes.windll.kernel32.CloseHandle(handle)
Well Python is open source, you are free to take that pthread function from 2.6 and move it into your own code or use it as a reference to implement your own.
For reasons that should be obvious there's no way to have a hybrid of Python that can import portions of newer versions.