Pass arguments to fortran exe with Python

[sambarluc]

Hi everybody,
this is a very newbie question, I guess. I do not have experience with scripting languages, but I am trying to learn Python, and use lots of fortran code in my work. So, let's say that I am not used to high level programming. What I expect Python to do, is something like: run a fortran code, give it the parameters it needs, process the output from fortran with another script and then cat a series of files together.
I guess this is not a very exotic task, but I can't find a tutorial or something like that focusing on this kind of things.
I am getting a bit lost in the documentation, I fear...
Thanks!

AC

[ghostdog74]

to call external programs, use the subprocess module.

[WW]

Expanding on ghostdog74's suggestion to use the subprocess (http://docs.python.org/library/subprocess.html) module...

To simply run a command, you can use the call() method:


>>> import subprocess
>>> subprocess.call(['ls','-a'])
. .. a.txt stuff.dat
0
>>>

If you want to get the output of the command into Python, use Popen():


>>> p = subprocess.Popen(['ls','-a'],stdout=subprocess.PIPE)
>>> result = p.stdout.readlines()
>>> result
['.\n', '..\n', 'a.txt\n', 'stuff.dat\n']
>>>

[sambarluc]

Wow, finally I am getting closer to what I want. Thanks!
But what about the input prompt of fortran? The fortran exe that I call asks for some parameters at the prompt. I have seen some module that emulate typing, but that seems a very complicated solution.
AC

[the_unforgiven]

Wow, finally I am getting closer to what I want. Thanks!
But what about the input prompt of fortran? The fortran exe that I call asks for some parameters at the prompt. I have seen some module that emulate typing, but that seems a very complicated solution.
AC
You can use the Popen.stdin for it.
For example:


proc = subprocess.Popen(['passwd'], shell=True, close_fds=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
print proc.stdout.readlines()
proc.stdin.write('newpasswd')
print proc.stdout.readlines()
proc.stdin.write('newpasswd')
status = proc.wait()
if status == 0:
print "Password changed successfully"

BIG FAT WARNING: This should be used carefully; I needed a program that reads input from stdin, so, I chose passwd - which was the first thing that came to my mind.

For more details, check out the examples given at the end of this page:
http://docs.python.org/library/subprocess.html

HTH ;)

[sambarluc]

Thank you very much, I think I have all the pieces of the puzzle, now.
AC