Cecil Westerhof wrote:
> I want to get the first 6 lines of ps output. For this I use:
> ========================================================================
> from subprocess import check_output
>
> ps_command = ('ps', '-eo', 'user,pid,pcpu,pmem,stat,start,time,cmd',
> '--sort') message = '\n'.join(check_output(ps_command +
> ('-%cpu',)).decode("utf-8").splitlines()[0:6])
> ========================================================================
>
> It works, but does not look very efficient. Is there a better way to
> do this?
Efficiency be damned, readability counts ;)
With that in mind here's a little code cleanup:
import subprocess
def text_head(text, n):
return "\n".join(text.split("\n", n)[:n])
def ps(sort=None):
cmd = ['ps', '-eo', 'user,pid,pcpu,pmem,stat,start,time,cmd']
if sort is not None:
cmd += ["--sort", sort]
return subprocess.check_output(cmd, universal_newlines=True)
if __name__ == "__main__":
print(text_head(ps("-%cpu"), 6))
For long strings and small n text.split(\n", n)[:n] is a bit faster than
text.splitlines()[n]
$ wc -l fodder.txt
969 fodder.txt
$ python3 -m timeit -s 'text = open("fodder.txt").read()' 'text.split("\n",
6)[:6]'
100000 loops, best of 3: 7.54 usec per loop
$ python3 -m timeit -s 'text = open("fodder.txt").read()' 'text.splitlines()
[:6]'
1000 loops, best of 3: 215 usec per loop
but the effect on the total time to run the code should be negligable.
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