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Debajyoti
Asked: 2020-11-08 07:55:29 +0800 CST

How to run a Fortran Executable file, which generally runs in Ubuntu Terminal, within a Python-3 script?

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I have a Fortran Executable file named chuck in the folder /home/debajyoti/chuckDir/.

The program chuck do is like, it takes an input file inputfile.txt and an output file outputfile.txt and calculates on the data from inputfile.txt and writes the output in the file outputfile.txt.

I to do all these calculations with the following steps in Ubuntu Terminal:

~$ cd chuckDir

~/chuckDir$ ./chuck <inputfile.txt> outputfile.txt

NOW I want to run chuck and do all these within a Python Script. The purpose of the Python3 Script is, it takes the data from the outputfile.txt to Plot. Now my question is how can I run chuck within the Python3 Script itself?

scripts gnome-terminal python python3 fortran

1 Answers

  1. This is usually where subprocess is a very useful bit of Pythonic magic.

    Assuming the input file is named inputfile.txt you can do this and throw stderr output on error, and stdout on successful run:

    import subprocess as sp  # I do this for shortening things later on
import shlex

# Run the program you want with the arguments you want split properly (thanks to shlex.split to making it so sp.run works right); store stdout and stderr results as well
chuck = sp.run(shlex.split('/full/path/to/chuck /full/path/to/inputfile.txt /full/path/for/outputfile.txt'), stdout=sp.PIPE, stderr=sp.PIPE)

if chuck.returncode != 0:
    # If a program exits on an error or fail condition its exitcode is usually not 0
    raise RuntimeError("Chuck did not run right!\n\n{}".format(chuck.stderr))

print(chuck.stdout)

    However, you need to really make sure that you are using proper paths for your files and the chuck executable in this, and use full directory paths. This is the basic code you'll need to work with it and to execute chuck with proper paths. You should use fully qualified paths on disk where possible, by the way.

    Essentially the extra steps to check the returncode, stderr output, and stdout output from the program are debugging steps. If the program runs as intended, you will get an outputfile.txt where you specify it to go.

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