How do I extract a column from text using Python?

Question

Could anybody please help me to get only the second column as output of ps aux command (i.e, only the PID column).

# script to print the processid
import os
import commands

out = commands.getoutput('ps aux')  # to get the process listing in out
# print out
# print out[2]  # print only second column from out
print out[:2]

Output of print out statement

    USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
    root         1  0.0  0.0   5728  1068 ?        Ss   Oct13   0:07 /sbin/init
    root         2  0.0  0.0      0     0 ?        S<   Oct13   0:00 [kthreadd]
    root         3  0.0  0.0      0     0 ?        S<   Oct13   0:00 [migration/0]
    root         4  0.0  0.0      0     0 ?        S<   Oct13   0:11 [ksoftirqd/0]
    root         5  0.0  0.0      0     0 ?        S<   Oct13   0:00 [watchdog/0]
    root         6  0.0  0.0      0     0 ?        S<   Oct13   0:00 [migration/1]

Thanks in advance

This is actually very easy using AWK if you have access to it. ps aux | awk {'print $1'} — Russell Dias
– Russell Dias, Commented Oct 20, 2011 at 4:54
@RussellDias you mean ps aux | awk '{print $2}' ($0 is full line, so $1 is the first column, not second...) — Tom
– Tom, Commented Oct 20, 2011 at 5:21
@Tom: Doh! I had $2 but changed it to $1 for some odd reason (I think I tested it on cygwin which does not output USER) :( eh can't update it now — Russell Dias
– Russell Dias, Commented Oct 20, 2011 at 5:24
@ANV you probably want to use out = subprocess.check_output('ps aux') too. The commands module is deprecated. — Tom
– Tom, Commented Oct 20, 2011 at 5:27

Tom · Accepted Answer · 2011-10-20 05:31:22Z

3

Use split() and splitlines() (to convert the string into a list of lines, and the list of lines into a list of columns that you can then index as needed):

>>> for line in out.splitlines():
...     fields = line.split()
...     if len(fields) >= 2:
...         print fields[1]


PID
1
2
3
4
5
6

edited Oct 20, 2011 at 5:31

Tom

44.9k35 gold badges101 silver badges103 bronze badges

answered Oct 20, 2011 at 4:55

Raymond Hettinger

229k67 gold badges405 silver badges504 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

ANV Over a year ago

Thanks for the answer. My actual need is to print the last column which is the command column. If we try the method you suggested then we get only the portion of the command column. eg:- the command column has got line as /bin/bash /bin/test.txt but it only prints /bin/bash. i wanted actually the whole command column. any suggestions would be helpful.Once again thank you for your help.

Raymond Hettinger Over a year ago

That is simple enough. Either print line[65:] or fields[10:].

ANV Over a year ago

Thanks exactly that's what i am looking for. If you don't mind, could you please let me know how you got the count(ie 65). Regarding fields i understood its the 10 value in the list field.

Tom Over a year ago

line is a string, so line[65:] is everything in line from character number 65 onwards. I presume @RaymondHettinger found that out by counting them or cutting and pasting and using len("...")...

Tom · Accepted Answer · 2011-10-23 22:18:06Z

3

As mentioned in the comments this is very straightforward to do using awk:

ps aux | awk {'print $2'}

However, here is also a python solution using a list comprehension, which gives you a list of PID's:

>>> [col.split()[1] for col in out.splitlines()]
['PID', '1', '2', '3', '4', '5', '6']

edited Oct 23, 2011 at 22:18

Tom

44.9k35 gold badges101 silver badges103 bronze badges

answered Oct 20, 2011 at 5:17

Russell Dias

73.9k5 gold badges58 silver badges72 bronze badges

Comments

iamawesome · Accepted Answer · 2025-05-16 16:42:35Z

0

import subprocess

out = subprocess.check_output(['ps', 'aux']).decode('utf-8') # run command and decode output

lines = out.strip().split('\n') # split in lines

for line in lines[1:]:
    columns = line.split()
    if len(columns) > 1:
        print(columns[0])  # based on the columns[key] you can extract the specific or convert to list

answered May 16 at 16:42

iamawesome

6628 silver badges15 bronze badges

Collectives™ on Stack Overflow

How do I extract a column from text using Python?

3 Answers 3

4 Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related