Re: subprocess.Popen howto?
Øystein ;
Down below: change yourPy.py to | yourPy.py
I just noticed the typo.
Sorry
Steve
norseman wrote:
Øystein Johansen (OJOHANS) wrote:
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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of the
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delete
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Thank you.
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If you don't like a lot of typing that obscures the process,
take a look at os.Popen2 Pg.39 or so in Lib.pdf for 2.5.2
In this case - the popen3 is probably your best bet.
I took a test run on subprocess a few months ago. My review:
excessive typing to accomplish the simple. BlackBox stuff is supposed
to be short and sweet.
BlackBox was the term applied to drivers and couplers back when.
Back when: one started by writing a subroutine that got used.
next one got to write a program
next one got to write an application
then a BlackBox
from there one could graduate to OS
That was back when!
to repeat from another of my postings:
---
processPython 2.5.2 (r252:60911, Mar 4 2008, 10:40:55)
[GCC 3.3.6] on linux2
Type help, copyright, credits or license for more information.
import os
AbWd = os.spawnlp( os.P_WAIT,abiword,abiword,)
The P_WAIT stops python until the program (abiword in this case)
completes. The at the end are for tokens to be given to the program
and yes - contrary to manual, the program MUST be there TWICE (complete
with any path needed).
for windows this works:
(for cut and paste from cmd.exe, see:
Re: Copy Paste in a Dos box from norseman 05/06/2009 4:28PM
)
Python 2.5.1 ... on win32
import os
result = os.spawnl( os.P_WAIT, d:\\winmcad\\mcad,)
Runs the program mcad. Returns to python when mcad exits.
---
In your case: substitute ...your_compiled_c_program, yourPy.py)
at the obvious places.
In case this isn't clear;
method 1: py1.py starts compiled.c which redirects to yourPy.py
method 2: py1.py uses os.popen3(compiled.c...) the two work it out.
In either case the receiver at the end stays open until completion so
sleep() things are not needed. (may need to test for EOL and EOT)
HTH
Steve
norse...@hughes.net
--
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--
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Re: subprocess.Popen howto?
Carl Banks wrote: On May 7, 2:58 pm, norseman norse...@hughes.net wrote: If you don't like a lot of typing that obscures the process, take a look at os.Popen2 Pg.39 or so in Lib.pdf for 2.5.2 In this case - the popen3 is probably your best bet. I took a test run on subprocess a few months ago. My review: excessive typing to accomplish the simple. Hmm, I won't argue that it can be excessive typing, but I think its purpose isn't to accomplish the simple but to hit all the corners of subprocesses. What if you want os.system without the shell? What if you want popen with the shell? On Windows what if I want a subprocess without a console from a Python program in a console. Stuff like that. Shell? You lost me. Why would you even use Windows? Just kidding. Build the TSR and Start from Python or the bootup autostart and use it from Python or whatever. Those in Unix, put the after the program name in the starter to get it to background. Be sure to use P_NOWAIT in the starter. I still use os.system for QD stuff, but now use subprocess for everything else since I prefer thorough to short and sweet. As long as speed (volume vs time) isn't a problem - OK. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list == 1) That one has access to and can make for ones self choices is freedom. 2) As far as forcing a 'do all' into use is concerned, especially at the expense of removing others choices (Python notes say subprocess is supplanting popen et al), well... that is dictitorial, anti-freedom. 3) Consider this: a do all is as useful as driving a Ferrari on a Jeep Jamboree cross crountry race. Or chasing a Ferrari through paved mountain roads with a Jeep. The SUV is supposed to be a do all. Would you actually expect it to win either race? After all, they are all cars. Use/create the proper tool for the job. I do not know any good mechanics that have a monkey-wrench (a crescent) in their tool box. And all of them will tell you that the guy who picks one up and starts toward the car may be upset with the driver but he is not a mechanic. (Wrong tool of choice. Besides, should not have been available. :) (Use the long handle 1/2 socket drive ratchet. Weight, length and balance are just right. ;) Everybody - Read #1 one more time and make it (speak out loud) my way. If the client is happy, who cares how it was done? But don't force others (Python admins taking notes?) Steve -- http://mail.python.org/mailman/listinfo/python-list
subprocess.Popen howto?
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
---
The information contained in this message may be CONFIDENTIAL and is
intended for the addressee only. Any unauthorised use, dissemination of the
information or copying of this message is prohibited. If you are not the
addressee, please notify the sender immediately by return e-mail and delete
this message.
Thank you.
--
http://mail.python.org/mailman/listinfo/python-list
Re: subprocess.Popen howto?
Øystein Johansen (OJOHANS) wrote:
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
---
The information contained in this message may be CONFIDENTIAL and is
intended for the addressee only. Any unauthorised use, dissemination of the
information or copying of this message is prohibited. If you are not the
addressee, please notify the sender immediately by return e-mail and delete
this message.
Thank you.
--
http://mail.python.org/mailman/listinfo/python-list
If you don't like a lot of typing that obscures the process,
take a look at os.Popen2 Pg.39 or so in Lib.pdf for 2.5.2
In this case - the popen3 is probably your best bet.
I took a test run on subprocess a few months ago. My review:
excessive typing to accomplish the simple. BlackBox stuff is supposed
to be short and sweet.
BlackBox was the term applied to drivers and couplers back when.
Back when: one started by writing a subroutine that got used.
next one got to write a program
next one got to write an application
then a BlackBox
from there one could graduate to OS
That was back when!
to repeat from another of my postings:
---
processPython 2.5.2 (r252:60911, Mar 4 2008, 10:40:55)
[GCC 3.3.6] on linux2
Type help, copyright, credits or license for more information.
import os
AbWd = os.spawnlp( os.P_WAIT,abiword,abiword,)
The P_WAIT stops python until the program (abiword in this case)
completes. The at the end are for tokens to be given to the program
and yes - contrary to manual, the program MUST be there TWICE (complete
with any path needed).
for windows this works:
(for cut and paste from cmd.exe, see:
Re: Copy Paste in a Dos box from norseman 05/06/2009 4:28PM
)
Python 2.5.1 ... on win32
import os
result = os.spawnl( os.P_WAIT, d:\\winmcad\\mcad,)
Runs the program mcad. Returns to python when mcad exits.
---
In your case: substitute ...your_compiled_c_program, yourPy.py)
at the obvious places.
In case this isn't clear;
method 1: py1.py starts compiled.c which redirects to yourPy.py
method 2: py1.py uses os.popen3(compiled.c...) the two work it out.
In either case the receiver at the end stays open until completion so
sleep() things are not needed. (may need to test for EOL and EOT)
HTH
Steve
norse...@hughes.net
--
http://mail.python.org/mailman/listinfo/python-list
Re: subprocess.Popen howto?
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
--
http://blog.rebertia.com
--
http://mail.python.org/mailman/listinfo/python-list
Re: subprocess.Popen howto?
On May 7, 2:58 pm, norseman norse...@hughes.net wrote: If you don't like a lot of typing that obscures the process, take a look at os.Popen2 Pg.39 or so in Lib.pdf for 2.5.2 In this case - the popen3 is probably your best bet. I took a test run on subprocess a few months ago. My review: excessive typing to accomplish the simple. Hmm, I won't argue that it can be excessive typing, but I think its purpose isn't to accomplish the simple but to hit all the corners of subprocesses. What if you want os.system without the shell? What if you want popen with the shell? On Windows what if I want a subprocess without a console from a Python program in a console. Stuff like that. I still use os.system for QD stuff, but now use subprocess for everything else since I prefer thorough to short and sweet. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
