[IronPython] import subprocess

Eric.Wyler at bentley.com Eric.Wyler at bentley.com
Thu Jul 5 13:09:12 PDT 2007


Matt,

 

I had the same problem and ended up solving it by using
System.Diagnostics.Process instead of subprocess.  As far as I know,
subprocess doesn't work under IronPython.  I don't remember all of the
reasons as to why it doesn't work, but, for example, os.pipe doesn't
exist under IronPython like in CPython.

 

Unfortunately, it's a bit of extra work if you're using subprocess to
capture stdout, stdin, etc.  Here's a snippet of some code I used for
this.  It's not very straightforward, unfortunately, because I wanted to
combine the stdout/stderr streams.  Also, the only way to run a command
like you would type it on the command line is to run it through cmd.exe.
You can search around for it, getting return values can be a real pain
as well.  I didn't test this code, just tried to copy and paste the
important parts from what I have, so I may have forgotten something.

 

class Process :

    def __init__( self ):

  self.stdoutstderr = System.IO.StringWriter()

  self.cmdLine = "rd /s /q ."

 

    def Run( self ):

        processStartInfo = System.Diagnostics.ProcessStartInfo( "cmd",
"/c " + self.cmdLine )

        processStartInfo.UseShellExecute = False

        processStartInfo.RedirectStandardInput = True

        processStartInfo.RedirectStandardOutput = True

        processStartInfo.RedirectStandardError = True

        processStartInfo.CreateNoWindow = True

        processStartInfo.EnvironmentVariables.Clear()

        for envVariable in os.environ.keys() :

            processStartInfo.EnvironmentVariables.Add( envVariable,
os.environ[ envVariable ] )

        processToRun = System.Diagnostics.Process()

        processToRun.StartInfo = processStartInfo

        processToRun.OutputDataReceived += self.__WriteStdoutData

        processToRun.ErrorDataReceived += self.__WriteStderrData

        processToRun.Start()

        processToRun.BeginOutputReadLine()

        processToRun.BeginErrorReadLine()

        processToRun.WaitForExit()

 

        stdoutstderrReader = System.IO.StringReader(
self.stdoutstderr.ToString() )

        return ( processToRun.StandardInput, stdoutstderrReader )

 

    def __WriteStdoutData ( self, sendingProcess, stdoutData ) :

        if stdoutData.Data != None:

            self.stdoutstderr.Write( stdoutData.Data + '\n' )

 

    def __WriteStderrData ( self, sendingProcess, stderrData ) :

        if stderrData.Data != None:

            self.stdoutstderr.Write( stderrData.Data + '\n' )

 

Hopefully that helps.

 

Eric

 

-----Original Message-----
From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Matthew S
Bourdua
Sent: Thursday, July 05, 2007 3:50 PM
To: users at lists.ironpython.com
Subject: [IronPython] import subprocess

 

Hello, 

 

I have a question about the "subprocess" module.  I am unable to "import


subprocess" in my scripts.  Will IronPython will support this in the
future, 

or, perhaps is it intentionally not supported?  (Or perhaps I am doing 

something stupid, and it should work?) 

 

I recently began using IronPython because I had both Python scripts and
.Net 

classes that I needed to use together.  So far I have been pretty
pleased 

with how well everything is working. 

 

My biggest problem has been that the os.system() call does not work in 

IronPython.  I notice that this was raised as an issue in Sep '06 

(http://www.codeplex.com/IronPython/WorkItem/View.aspx?WorkItemId=2982).


While hunting around for an alternative, I found the following text in
the 

library reference (http://docs.python.org/lib/module-subprocess.html): 

 

"The subprocess module ... intends to replace several other, older
modules 

and functions, such as: 

 

os.system

os.spawn*

os.popen*

popen2.*

commands.*" 

 

For this reason, I thought that perhaps "os.system" was going to become 

deprecated in favor of "subprocess", and that might explain why this
issue 

has not been addressed. 

 

However, I am unable to "import subprocess" in IronPython.  When I do
so, an 

exception is raised because, "No module named fcntl".  Digging into this
a 

bit, I notice the following variable defined within subprocess.py (this
is 

from ActivePython 2.5): 

 

mswindows = (sys.platform == "win32") 

 

And then many conditional statements of the form:

if mswindows:

...#Windows specific code

else

...#Non-windows code, presumably 

 

IronPython fails this check because sys.platform = 'cli', and thus is
lead 

into using modules that are (I would guess) meant for Unix-based
systems. 

 

Further, this behavior seems to be known - I noticed that this seemed to
be 

accounted for in (what appears to be) the automatic test-suite code
located 

here:

http://www.codeplex.com/IronPython/SourceControl/FileView.aspx?itemId=29
6023 

&changeSetId=21805 

 

What's strange to me is that I couldn't find a single reference to using


subprocess in IronPython anywhere.  So perhaps this issue is widely 

understood by everybody but me (I'm relatively new to Python), or simply
not 

an issue for anybody but me? 

 

Anyway, I was hoping somebody on this mailing list might have some
insight 

to share. 

 

Thanks,

Matt

 

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