How to wrap the shell command in os.system of Python?

Question

It can get a file named myFile.txt, in which the content is:

file  '/home/debian/1.flv'  
file  '/home/debian/2.flv'  
file  '/home/debian/3.flv'  
file  '/home/debian/4.flv'  
file  '/home/debian/5.flv'

Now I want to wrap it in Python

os.system("seq  --format="file  '/home/debian/%G.flv'" 5 > myFile.txt" )    
File "<stdin>", line 1  
os.system("seq  --format="file  '/home/debian/%G.flv'" 5 > myFile.txt" )  
                             ^
SyntaxError: invalid syntax

How to Wrap it in Python?

I do understand how to create the file in Python (kvivek)
It is my target to understand how to use complicated shell command in Python,
If the number of lines is a variable?

There is still a problem with

@Torxed escape character way

>>> i=7    
>>> os.system("seq --format=\"file '/home/debian/%G.flv'\" %d > myFile.txt" %i )  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
TypeError: float argument required, not str

@ganachoco's triple quotes way

>>> os.system('''seq  --format="file  '/home/debian/%G.flv'" %d > myFile.txt" %i''')  
sh: 1: Syntax error: Unterminated quoted string

there are two staus to be considered, status 1: the variable is in the shell, we can do (I had verified the following tow shell commands)

root@debian:/home/debian# i=7
root@debian:/home/debian# seq --format="file '/home/debian/%G.flv'" $i > myFile.txt

How to wrap it in Python with os.system?

>>> os.system('i=7')
0
>>> os.system("seq --format=\"file '/home/debian/%G.flv'\" $i > myFile.txt")
seq: missing operand
Try `seq --help' for more information.
256

The variable is in the Python, now I want to call the shell command to put the variable from Python into the shell, how can I do?

>>> i=7  #in python prompt
>>> os.system("seq --format=\"file '/home/debian/%G.flv'\" `here i want to get value from python prompt` > myFile.txt")

os.system("seq --format=\"file '/home/debian/%G.flv'\" 5 > myFile.txt" ) ? — Torxed
– Torxed, Commented Feb 11, 2013 at 10:01

Alex L · Accepted Answer · 2013-02-11 10:01:39Z

3

use triple quote

os.system("""seq  --format="file  '/home/debian/%G.flv'" 5 > myFile.txt""")

edited Feb 11, 2013 at 10:01

Alex L

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answered Feb 11, 2013 at 10:00

ganachoco

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Comments

Vorsprung · Accepted Answer · 2013-02-11 16:50:20Z

3

quote the " with a backslash

for i in (range(1,5)):
    os.system("seq  --format=\"file  '/home/debian/%d.flv'\" > myFile.txt" %i )

edited Feb 11, 2013 at 16:50

answered Feb 11, 2013 at 10:00

Vorsprung

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Comments

kvivek · Accepted Answer · 2013-02-11 12:15:20Z

0

Hope this gives is what you are looking for

[root@localhost ~]# python
Python 2.6.6 (r266:84292, Apr 11 2011, 15:50:32)
[GCC 4.4.4 20100726 (Red Hat 4.4.4-13)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> cmdstr = """i=7 && seq --format="file '/home/kvivek/%G.flv'" $i > myFile.txt"""
>>> os.system(cmdstr)
0
>>> exit()
[root@localhost ~]# cat myFile.txt
file '/home/kvivek/1.flv'
file '/home/kvivek/2.flv'
file '/home/kvivek/3.flv'
file '/home/kvivek/4.flv'
file '/home/kvivek/5.flv'
file '/home/kvivek/6.flv'
file '/home/kvivek/7.flv'
[root@localhost ~]#

edited Feb 11, 2013 at 12:15

answered Feb 11, 2013 at 10:10

kvivek

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