Ouestion: … a way to check if a process is still running … You can do it for instance: p = subprocess.Popen(… “”” A None value indicates that the process hasn’t terminated yet. “”” poll = p.poll() if poll is None: # p.subprocess is alive Python ยป 3.6.1 Documentation popen-objects Tested with Python:3.4.2
Depending on how you want to work your script you have two options. If you want the commands to block and not do anything while it is executing, you can just use subprocess.call. #start and block until done subprocess.call([data[“om_points”], “>”, diz[‘d’]+”/points.xml”]) If you want to do things while it is executing or feed things into … Read more
The subprocess module lets you run and control other programs. Anything you can start with the command line on the computer, can be run and controlled with this module. Use this to integrate external programs into your Python code. The multiprocessing module lets you divide tasks written in python over multiple processes to help improve … Read more
Some rules of thumb for subprocess. Never use shell=True. It needlessly invokes an extra shell process to call your program. When calling processes, arguments are passed around as lists. sys.argv in python is a list, and so is argv in C. So you pass a list to Popen to call subprocesses, not a string. Don’t … Read more
According to the subprocess.check_output() docs, the exception raised on error has an output attribute that you can use to access the error details: try: subprocess.check_output(…) except subprocess.CalledProcessError as e: print(e.output) You should then be able to analyse this string and parse the error details with the json module: if e.output.startswith(‘error: {‘): error = json.loads(e.output[7:]) # … Read more
A Popen object has a .wait() method exactly defined for this: to wait for the completion of a given subprocess (and, besides, for retuning its exit status). If you use this method, you’ll prevent that the process zombies are lying around for too long. (Alternatively, you can use subprocess.call() or subprocess.check_call() for calling and waiting. … Read more
To get the output of ls, use stdout=subprocess.PIPE. >>> proc = subprocess.Popen(‘ls’, stdout=subprocess.PIPE) >>> output = proc.stdout.read() >>> print output bar baz foo The command cdrecord –help outputs to stderr, so you need to pipe that indstead. You should also break up the command into a list of tokens as I’ve done below, or the … Read more
The definition of subprocess.call() clearly mentions: It is equivalent to: run(…).returncode (except that the input and check parameters are not supported) As the Python 3.5’s subprocess document says: Prior to Python 3.5, these three functions (i.e. .call(), .check_call(), .check_output()) comprised the high level API to subprocess. You can now use run() in many cases, but … Read more
In Python 3.5+ to redirect the output, just pass an open file handle for the stdout argument to subprocess.run: # Use a list of args instead of a string input_files = [‘file1’, ‘file2’, ‘file3’] my_cmd = [‘cat’] + input_files with open(‘myfile’, “w”) as outfile: subprocess.run(my_cmd, stdout=outfile) As others have pointed out, the use of an … Read more
The b indicates that what you have is bytes, which is a binary sequence of bytes rather than a string of Unicode characters. Subprocesses output bytes, not characters, so that’s what communicate() is returning. The bytes type is not directly print()able, so you’re being shown the repr of the bytes you have. If you know … Read more