2009/5/7 Øystein Johansen (OJOHANS) <ojoh...@statoilhydro.com>:
> 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?
import subprocess
subprocess.call(["./mycalc"]) # add `bufsize=-1` as argument to have
output be buffered
#process inherits our filehandles and writes directly to them
#.call() only returns once the process has exited
Cheers,
Chris
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