Gordon Fontenot Gordon Fontenot - 3 months ago 6
Python Question

Any way to assign terminal output to variable with python?

I need to grab the duration of a video file via python as part of a larger script. I know I can use ffmpeg to grab the duration, but I need to be able to save that output as a variable back in python. I thought this would work, but it's giving me a value of 0:

cmd = 'ffmpeg -i %s 2>&1 | grep "Duration" | cut -d \' \' -f 4 | sed s/,//' % ("Video.mov")
duration = os.system(cmd)
print duration


Am I doing the output redirect wrong? Or is there simply no way to pipe the terminal output back into python?

Answer

os.system returns a return value indicating the success or failure of the command. It does not return the output from stdout or stderr. To grab the output from stdout (or stderr), use subprocess.Popen.

import subprocess
proc=subprocess.Popen('echo "to stdout"', shell=True, stdout=subprocess.PIPE, )
output=proc.communicate()[0]
print output

See the wonderfully written Python Module of the Week blog.

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