Running an outside program executable in Python

Question

I just started working on Python  and I have been trying to run an outside executable from Python   I have an executable for a program written in Fortran  Let   s say the name for the executable is flow exe  And my executable is located in C  Documents and Settings flow model  I tried both os system and popen commands  but so far I couldn t make it work  The following code seems like it opens the command window  but it wouldn t execute the model     Import system modules import sys  string  os  arcgisscripting os system  C  Documents and Settings flow model flow exe     How can I fix this

User · Answer

Try  import subprocess subprocess call   C  Documents and Settings flow model flow exe

User · Answer

Those whitespaces can really be a bother   Try os chdir  C  Documents  and  Settings    followed by relative paths for os system  subprocess methods  or whatever    If best-effort attempts to bypass the whitespaces-in-path hurdle keep failing  then my next best suggestion is to avoid having blanks in your crucial paths   Couldn t you make a blanks-less directory  copy the crucial  exe file there  and try that   Are those havoc-wrecking space absolutely essential to your well-being

User · Answer

import os path    C  Documents and Settings flow model   os chdir path  os system  flow exe

User · Answer

If using Python 2 7 or higher  especially prior to Python 3 5  you can use the following   import subprocess    subprocess call args     stdin None  stdout None  stderr None  shell False  Runs the command described by args  Waits for command to complete  then returns the returncode attribute  subprocess check call args     stdin None  stdout None  stderr None  shell False  Runs command with arguments  Waits for command to complete  If the return code was zero then returns  otherwise raises CalledProcessError  The CalledProcessError object will have the return code in the returncode attribute   Example  subprocess check call  r C  pathToYourProgram yourProgram exe    your    arguments    comma    separated        In regular Python strings  the  U character combination signals a   extended Unicode code point escape    Here is the link to the documentation  http   docs python org 3 2 library subprocess html  For Python 3 5  you can now use run   in many cases  https   docs python org 3 5 library subprocess html subprocess run

User · Answer

for the above question this solution works     just change the path to where your executable file is located    import sys  string  os  os chdir  C   Downloads  xpdf-tools-win-4 00  xpdf-tools-win-4 00  bin64    os system  C   Downloads  xpdf-tools-win-4 00  xpdf-tools-win-4 00 bin64  flowwork exe        import sys  string  os  os chdir  C   Downloads  xpdf-tools-win-4 00  xpdf-tools-win-4 00  bin64    os system r C   Downloads  xpdf-tools-win-4 00  xpdf-tools-win-4 00 bin64  pdftopng exe test1 pdf rootimage        Here test1 pdf rootimage is for my code

User · Answer

There are loads of different solutions  and the results will strongly depend on    the OS you are using  Windows  Cygwin  Linux  MacOS the python version you are using  Python2 or Python3x   As I have discovered some things that are claimed to work only in Windows  doesn t  probably because I happen to use Cygwin which is outsmarting the OS way to deal with Windows paths  Other things only work in pure  nix based OS s or in Python2 or 3    Here are my findings     Generally speaking  os system   is the most forgiving method  os startfile   is the least forgiving   Windows only  amp  amp  if you re lucky  subprocess Popen        not recommended subprocess run winView  shell True  the recommended way  Remembering that using subprocess for anything may pose a security risk    Try these   import os  subprocess     winView     cygdrive c Windows explorer exe  s    somefile       chose one of these  os system winView  subprocess Popen    cygdrive c Windows explorer exe    somefile png    subprocess run winView  shell True    Q  Why would you want to use explorer in Windows    A  Because if you just want to look at the results of some new file  explorer will automatically open the file with whatever default windows program you have set for that file type  So no need to re-specify the default program to use

User · Answer

If it were me  I d put the EXE file in the root directory  C   and see if it works like that  If so  it s probably the  already mentioned  spaces in the directory name  If not  it may be some environment variables   Also  try to check you stderr  using an earlier answer by int3    import subprocess process   subprocess Popen   C  Documents and Settings flow model flow exe                                 stderr   subprocess PIPE  if process stderr      print process stderr readlines     The code might not be entirely correct as I usually don t use Popen or Windows  but should give the idea  It might well be that the error message is on the error stream

User · Answer

in python 2 6 use string enclosed inside quotation   and apostrophe   marks  Also a change single   to double      Your working example will look like this   import os os system   C   Documents and Settings  flow model  flow exe       Also You can use any parameters if Your program ingest them   os system  C    Program Files  x86    Maxima-gcl-5 37 3  gnuplot  bin  gnuplot -e  plot  -10 10  sin x  atan x  cos atan x    pause mouse      finally You can use string variable  as an example is plotting using gnuplot directly from python   this program  C    Program Files  x86    Maxima-gcl-5 37 3  gnuplot  bin  gnuplot   this par  -e  set polar  plot  -2 pi 2 pi   -3 3   -3 3  t sin t   pause -1   os system this program     this par

User · Answer

I d try inserting an  r  in front of your path if I were you  to indicate that it s a raw string - and then you won t have to use forward slashes  For example   os system r C  Documents and Settings flow model flow exe

User · Answer

That s the correct usage  but perhaps the spaces in the path name are messing things up for some reason   You may want to run the program under cmd exe as well so you can see any output from flow exe that might be indicating an error

User · Answer

Your usage is correct  I bet that your external program  flow exe  needs to be executed in its directory  because it accesses some external files stored there   So you might try   import sys  string  os  arcgisscripting os chdir  c   documents and settings  flow model   os system   C   Documents and Settings  flow model  flow exe       Beware of the double quotes inside the single quotes

User · Answer

By using os system   import os os system r  C  Documents and Settings flow model flow exe

User · Answer

Use subprocess  it is a smaller module so it runs the  exe quicker   import subprocess subprocess Popen  r U  Year 8 kerbal space program KSP exe

User · Answer

Is that trying to execute C  Documents with arguments of  and    Settings flow model flow exe    Also  you might consider subprocess call

User · Answer

The simplest way is   import os os startfile  C  Documents and Settings flow model flow exe     It works  I tried it

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