I have a command in python:
os.system('echo {{"value": {0:0.0f}}} | /usr/bin/cmd -parameters'.format(value)) the thing is that I receive value instead of "value". I would like to have "value" in shell. I've tried with triple double quotes, with slashes and json.dumps. Nothing helped, still value instead of "value".
Could you help me?
os.system is deprecated. Use subprocess instead, which will handle the quoting nicely for you.
Since you have a pipe, you would normally have to create 2 subprocess objects, but here you just want to feed standard input so:
import subprocess p = subprocess.Popen(["/usr/bin/cmd","-parameters"],stdin=subprocess.PIPE) p.communicate('{{"value": {:0.0f}}}\n'.format(value).encode()) # we need to provide bytes rc = p.wait() The quoting issue is gone, since you're not using a system command to provide the argument, but pure python.
to test this I have changed the command to more so I can run it on windows (which also proves that this is portable):
import subprocess value=12.0 p = subprocess.Popen(["more.com"],stdin=subprocess.PIPE) p.communicate('{{"value": {:0.0f}}}\n'.format(value).encode()) rc = p.wait() that prints: {"value": 12}
value is still unquoted in the output. You need to escape the double quotes around value{value: 12} on mac with python 3.7.0.encode() for it to work (the first time I had forgotten it). Have you tried the "more" example without any changes?If you want to echo quotes, you need to escape them.
For example:
echo "value" value
echo "\"value\"" "value"
So your python code should look like
os.system('echo {{\\"value\\": {0:0.0f}}} | /usr/bin/cmd -parameters'.format(value)) Note, that you should use double slashes \\ because python would escape a single slash.
subprocessso the quoting is handled for you