how to launch a executable in python without blocking the python execution

Question

In linux, I have a executable, that should be run like this: ./a.exe inputdata

I want to launch this executable in my python script, but I do not want to block the rest of the python code.

I tried soemthing like this, but

# launch sensor node
def launchA():
    subprocess.Popen(["Path/a.exe", inputdata])

if __name__ == '__main__':
    p = multiprocessing.Process(target=launchA,args=())
    p.start()
    print("sensorlaunched")

However, the luanchA process still blocks the print function.

What went wrong in my code? Thanks!

You've used the .exe extension on a Linux binary? That's heresy! — Fred Foo
– Fred Foo, Commented Feb 29, 2012 at 16:55

Fred Foo · Accepted Answer · 2012-02-29 16:56:16Z

3

What you're doing is pure overkill: you're creating a process with multiprocessing to manage a process created with subprocess. Just use subprocess alone:

p = subprocess.Popen(["Path/a.exe", inputdata])

Now p is a handle referring to the running a.exe process and your script can continue doing what it was doing.

answered Feb 29, 2012 at 16:56

Fred Foo

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5 Comments

Xing Fan Over a year ago

I just tired "p = subprocess.Popen(["Path/a.exe", inputdata])", but it still blocks the print function... The a.exe grabs the terminal, and I do not see print("hello") function is exectuted...

Sven Marnach Over a year ago

@XingFan: a.exe and the original process write to the same terminal, but no process "grabs" it. Having two simultaneously running processes writing to the same terminal will certainly mix the two data streams in a non-deterministic way, but that does mean the original process blocks.

Xing Fan Over a year ago

I c. Thanks! But I tried to add "&" in the command,like this p = subprocess.Popen(["Path/a.exe", inputdata],"&") to release the terminal, but I still do not see the print function is executed.........

Fred Foo Over a year ago

@XingFan: that & doesn't do anything. The fact that nothing changes means the issue is not with subprocess.

Sven Marnach Over a year ago

@XingFan: There is no such thing as "releasing the terminal". The terminal isn't owned by any process. And adding a random "&" as parameter to Popen() will lead to an error.

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