subprocess.Popen howto?

[Øystein Johansen (OJOHANS)]

Hi,
 
I have problems understanding the subprocess.Popen object. I have a iterative calculation in a process running and I want to pipe the output (stdout) from this calculation to a Python script.
 
Let me include a simple code that simulates the calculating process:
/* This code simulates a big iterative calculation */
#include <stdio.h>
#include <math.h>
 
int main()
{
 float val[2] = { M_PI, M_E };
 int i;
 
 for ( i = 0; i < 2 i++) {
  sleep( 15 );   /* It's a hard calculation. It take 15 seconds */
  printf("Value: %5.6f\n", val[i] );
  fflush( stdout );
 }
 return 0;
}
 
let's compile this to mycalc: gcc -o mycalc calc.c ... (untested code)
 
In C I have this code which starts the mycalc process and handles the output from it:
 
#include <stdio.h>
#include <assert.h>
#define BUF_SIZE 256
 
int main()
{
 FILE *pip;
 char line[BUF_SIZE];
 
 pip = popen("mycalc", "r");
 assert( pip != NULL );
 
 while ( fgets( line, BUF_SIZE, pip )) {
  printf( "Hello; I got: %s \n", line );
  fflush( stdout );
 }
 pclose( pip );
 return 0;
}

How can I make such while-loop in Python? I assume I should use subprocess.Popen(), but I can't figure out how?
 
-Øystein
 
 


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