how to assign variable value in python in terminal commands?

Question

My code:

import os
from xml.dom import minidom

doc = minidom.parse("jobs.xml")

job = doc.getElementsByTagName("job")[0]
id = job.getElementsByTagName("id")[0]
name = job.getElementsByTagName("name")[0]

id_data = id.firstChild.data
name_data = name.firstChild.data

os.system('curl --compressed -H "Accept: application/xml" -X GET "http://localhost:19888/ws/v1/history/mapreduce/jobs/"')
>>> /home/ankit/rrd-xml/task.xml

I want to get the commands like

os.system('curl --compressed -H "Accept: application/xml" -X GET "http://localhost:19888/ws/v1/history/mapreduce/jobs/< variable value of name_data >"') 
>>> /home/ankit/rrd-xml/task.xml

How can i do it in python itself?

What do you mean with I want to get the commands like...? It's not clear what you're asking. Do you meant the output of that call? Or the process ID of the spawned process, or something else? — Marcus Müller
– Marcus Müller, Commented Feb 7, 2016 at 10:33

mhawke · Accepted Answer · 2016-02-07 10:58:02Z

Use single quotes around the command, or even triple quotes, so that the quotes that form part of the command are not confused with the Python string:

os.system('curl --compressed -H "Accept: application/xml" -X GET "http://localhost:19888/ws/v1/history/mapreduce/jobs/{}" >> /home/ankit/rrd-xml/task.xml'.format(name_data))

That will work, but it's not the best. It would be better for you to use Python to make the HTTP request. requests is a good module for this:

import requests

url = 'http://localhost:19888/ws/v1/history/mapreduce/jobs/{}'.format(name_data)
headers = {'Accept': 'application/xml'}

response = requests.get(url, headers=headers)

with open('/home/ankit/rrd-xml/task.xml', 'a') as outfile:
    outfile.write(response.content)

This code will GET the URL, setting the Accept header to application/xml and append the response to the file. Compression is requested by default.

Dušan Maďar · Accepted Answer · 2016-02-07 10:41:13Z

1

What you want is a simple string formatting.

import os
from xml.dom import minidom

doc = minidom.parse("jobs.xml")

job = doc.getElementsByTagName("job")[0]
id = job.getElementsByTagName("id")[0]
name = job.getElementsByTagName("name")[0]

id_data = id.firstChild.data
name_data = name.firstChild.data

url = 'http://localhost:19888/ws/v1/history/mapreduce/jobs/{name}'.format(name=name_data)
cmd = 'curl --compressed -H "Accept: application/xml" -X GET "{url}"'.format(url=url)

os.system(cmd)

answered Feb 7, 2016 at 10:41

Dušan Maďar

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Comments

harishkb · Accepted Answer · 2016-02-07 11:51:17Z

0

Use subprocess. The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using the os.system function.

import subprocess
import shlex

command = shlex.split('curl --compressed -H "Accept: application/xml" -X GET http://localhost:19888/ws/v1/history/mapreduce/jobs/')

with open('/home/ankit/rrd-xml/task.xml', 'a') as f:
    subprocess.Popen(command, stdout=f)

edited Feb 7, 2016 at 11:51

answered Feb 7, 2016 at 10:42

harishkb

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3 Comments

mhawke Over a year ago

This won't work as is. You might want to split the command up into a list. Or, because of the redirection, set shell=True and hope that it is not insecure.

mhawke Over a year ago

That's still not going to work. For one thing, split() will split the header. shlex.split() might be better. Also, the IO redirection will not work. Either you need to open the output file and pass it to Popen as the child's stdout; or do not split the command string, set shell=True and open up a potential security risk.

harishkb Over a year ago

@mhawke thanks for that mate. Very useful info there. I wish I could upvote your comments but sadly I don't have enough points to do so. Cheers!

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