Is there a better way to execute commands in JSON running python

Question

Can somebody suggest a better way to execute multiple commands within JSON using Python.

For example how to improve the following:

JSON:

$ python -m json.tool test2.json

{
"command": "mkdir -p /home/ec2-user/data2/opt/ODS",
"command1": "mkdir -p /home/ec2-user/data4/opt/ODS",
"command2": "mkdir -p /home/ec2-user/data5/opt/ODS"
}

Python:

$ cat parse.py
   import json
   import sys
   import subprocess
   from pprint import pprint

   jdata = open(sys.argv[1])

   data = json.load(jdata)

   print "start"
   print(data)
   subprocess.call(data['command'], shell=True)
   subprocess.call(data['command1'], shell=True)
   subprocess.call(data['command2'], shell=True)
   print "end"
   jdata.close()

Output:

]$ python parse.py test2.json start {u'command1': u'mkdir -p /home/ec2-user/data4/opt/ODS', u'command2': u'mkdir -p /home/ec2-user/data5/opt/ODS', u'command': u'mkdir -p /home/ec2-user/data2/opt/ODS'} end

TIA

Hi daimne, try using a json structure that is an array ( or list ) , not a unordered hash. Then you can just iterate through the list in order and not pay attention to the keys ( command, command1, command2 are superfluous ) — Mark
– Mark, Commented Sep 18, 2017 at 18:17
I would suggest not doing it at all. If you are going to let your Python script execute arbitrary shell commands, just replace test2.json with a shell script and have Python execute it directly. — chepner
– chepner, Commented Sep 18, 2017 at 18:31
@Chepner: You could also accomplish the same result with a short shell script an no python code at all. — Mark
– Mark, Commented Sep 19, 2017 at 3:42
Yes, but I can picture a reason where the shell script is just a small part of what the Python script is doing. I see no reason to package individual lines of a shell script into a JSON file, only to be unpackaged again for execution. — chepner
– chepner, Commented Sep 19, 2017 at 12:26

Mark · Accepted Answer · 2017-09-18 18:23:09Z

1

Here's the structure and code you are looking for:

$ python -m json.tool test2.json
[
    "mkdir -p /home/ec2-user/data2/opt/ODS",
    "mkdir -p /home/ec2-user/data4/opt/ODS",
    "mkdir -p /home/ec2-user/data5/opt/ODS"
]

Python:

$ cat parse.py 
import json
import sys
import subprocess
from pprint import pprint

jdata = open(sys.argv[1])

data = json.load(jdata)

print "start"
print(data)
for command in data:
  subprocess.call(command, shell=True)
print "end"
jdata.close()

Output:

$ python parse.py test2.json
start
[u'mkdir -p /home/ec2-user/data2/opt/ODS', u'mkdir -p /home/ec2-user/data4/opt/ODS', u'mkdir -p /home/ec2-user/data5/opt/ODS']
end

answered Sep 18, 2017 at 18:23

Mark

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Comments

Yaroslav Surzhikov · Accepted Answer · 2017-09-18 18:20:18Z

0

In your example it would be better, to use os.makedirs.

But if you REALLY need subprocess module - i suggest you to exec command with single subprocess instance. For example:

subprocess.call('; '.join(data.values()), shell=True)

answered Sep 18, 2017 at 18:20

Yaroslav Surzhikov

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Comments

atwalsh · Accepted Answer · 2017-09-18 18:31:06Z

0

Similar to @Mark's answer, but keeping your original structure:

$ cat parse.py
import json
import sys
import 
from pprint import pprint

jdata = open(sys.argv[1])

data = json.load(jdata)

print "start"
print(data)
for command in data.values():                
  subprocess.call(command, shell=True)
print "end"
jdata.close()

edited Sep 18, 2017 at 18:31

answered Sep 18, 2017 at 18:26

atwalsh

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3 Comments

Yaroslav Surzhikov Over a year ago

Why do you iterate over keys and values if you need just values ? Dictionaries have .values() method for that

Mark Over a year ago

Is the order of value retrieval from the dictionary guaranteed? I think that the commands may not be executed in the order they were intended in the code above.

atwalsh Over a year ago

As long as the dict is not modified, yes. If there is still concern about order use .iteritems(). Docs here.

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