How to call the python variable into linux command

Question

I am writing python script, in my python script i want to run "list of files in a directory" using commands.getoutput, my probleam is "i defined the directory path in python variable like "dir_name".I tried with following.

dir_name="/user/pjanga/python_test"
index_list=commands.getoutput('ls -l',dir_name,'| 'wc -l')

Error:-

File "diii.py", line 10
    index_list=commands.getoutput('ls -l',dir_name,'| 'wc -l')
                                                        ^
SyntaxError: invalid syntax

Could you please help me out run?

I Think syntax highlighting says it all...

willeM_ Van Onsem
– willeM_ Van Onsem

2017-01-28 13:22:53 +00:00
Commented Jan 28, 2017 at 13:22 — willeM_ Van Onsem
– willeM_ Van Onsem, Commented Jan 28, 2017 at 13:22

cdarke · Accepted Answer · 2017-01-28 15:06:29Z

2

Several problems here, try:

index_list = commands.getoutput('ls -l ' + dir_name + ' | wc -l')

String concatenation is a +, not a comma, and you had an uneven number of single quotes. Note also the space after the ls -l.

However, there are far better ways to do this. First of all the answer does not represent the number of files in the directory. Do an ls -l on the command-line and you will see that the first line is "total", not a filename (this is historical and represents the number of blocks, and is pretty useless).

If you used ls instead of ls -l you would not get this issue.

However, there is no need to call two separate external programs, use python:

import os
index_list = len([name for name in os.listdir(dir_name) ])

Here we call os.listdir() and create a list of filenames, then just get the number of items in that list.

There are several other ways to do this in python.

edited Jan 28, 2017 at 15:06

answered Jan 28, 2017 at 14:53

cdarke

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Comments

Roshan · Accepted Answer · 2017-01-28 15:24:47Z

0

There are different ways to execute the command from python in Linux machine.

Method 1:

index_list = commands.getoutput('ls -l ' + dir_name + ' | wc -l')

Method 2:

import os
os.system("ls -l ' + dir_name + ' | wc -l')

Method 3:

import subprocess
index_list = subprocess.check_output('ls -l ' + dir_name + ' | wc -l, shell=True)

Hope it helps !!

answered Jan 28, 2017 at 15:24

Roshan

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