Linux shell to python

Philipp Hagemeister phihag at phihag.de
Mon Jul 30 13:59:15 CEST 2012


On 07/30/2012 01:31 PM, Jürgen A. Erhard wrote:
> On Mon, Jul 30, 2012 at 12:35:38PM +0200, Philipp Hagemeister wrote:
>> import subprocess
>> [ l.partition(' ')[0]      # or l[:7], if you want to copy it verbatim
>>   for l in subprocess.check_output(['lspci']).splitlines()
>>   if 'Q' in l and isp_str1 in l and isp_str2 in l
>> ]
> 
> Ouch.  A list comprehension spanning more than one line is bad code
> pretty much every time.

I didn't want to introduce a separate function, but as requested, here's
the function version:

def pciIds(searchWords=['Q', isp_str1, isp_str2]):
  for l in subprocess.check_output(['lspci']).splitlines():
    if all(sw in l for sw in searchWords):
        yield l.partition(' ')[0]

You could also separate the processing, like this:

lines = subprocess.check_output(['lspci']).splitlines()
lines = [l for l in lines if 'Q' in l and isp_str1 in l and isp_str2 in l]
# Or:
lines = filter(lambda l: 'Q' in l and isp_str1 in l and isp_str2 in l,
lines)


[l.partition(' ')[0] for l in lines]
# Or:
map(lambda l: l.partition(' ')[0], lines)

But personally, I have no problem with three-line list comprehensions.
Can you elaborate why the list comprehension version is bad code?

Or more to the point, how would *you* write it?

- Philipp


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