how to create dynamic configuration file using python

Question

I have a python script which is controlled by a config file called system.config .the structure of config file is like bellow with some default values.

[company]
companyname: XYZ

[profile]
name: ABC
joining: 1/1/2014

the code for config file is : config_parser_details.py

import ConfigParser
import sys

Config = ConfigParser.ConfigParser()
Config.read("system.config")
filename = "system.config"

def ConfigSectionMap(section):
  dict1 = {}
  options = Config.options(section)
  for option in options:    
    try:
      dict1[option] = Config.get(section, option)
      if dict1[option] == -1:
         DebugPrint("skip: %s" % option)
    except:
      print("exception on %s!" % option)
      dict1[option] = None
  return dict1

company = ConfigSectionMap("company")['companyname']
name = ConfigSectionMap("profile")['name']
joindate = ConfigSectionMap("profile")['joining']

now the code for my script is : test.py

import config_parser_details as p
import sys
import warnings
import os

company = p.company

name = p.name
date = p.joindate


print("%s\n" %company)
print("%s\n" %name)

output is

XYZ
ABC

now I want to give input in the config file through command line. like

python test.py --compname ="testing"

if any argument is missing in the command line than default value will be the input.

What is the expected output of python test.py --compname="testing" — sid1408
– sid1408, Commented Apr 17, 2015 at 10:41
in present condition in I ran python test.py the output is XYZ ABC and output of python test.py --compname ="testing" will be testing ABC. that is my goal — Arijit Panda
– Arijit Panda, Commented Apr 17, 2015 at 10:46
You want --compname="testing" to save the companyname as testing in your system.config and print the result. Right? — sid1408
– sid1408, Commented Apr 17, 2015 at 10:52
yes . in default companyname: XYZ so --compname="testing" will change the value of compname XYZ to testing. — Arijit Panda
– Arijit Panda, Commented Apr 17, 2015 at 11:01

Stéphane B. · Accepted Answer · 2015-04-17 14:11:39Z

1

You could use argparse library to parse command line arguments.

So your test.py file looks like below :

import config_parser_details as p
import sys
import warnings
import os
import argparse

commandLineArgumentParser = argparse.ArgumentParser()
commandLineArgumentParser.add_argument("-c", "--compname", help="Company name", default=p.company)
commandLineArguments = commandLineArgumentParser.parse_args()

company = commandLineArguments.compname

name = p.name
date = p.joindate

print("%s\n" %company)
print("%s\n" %name)

answered Apr 17, 2015 at 14:11

Stéphane B.

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Comments

manicphase · Accepted Answer · 2015-04-17 12:44:16Z

1

I'd advise looking into a tool like docopt.

For a quick fix though, you can try doing this

def ConfigSectionMap(section):
  options = Config.options(section)

  arg_dict = {}
  for command_line_argument in sys.argv[1:]:
    arg = command_line_argument.split("=")
    arg_dict[arg[0][2:]] = arg[1]

  for key in arg_dict:
    options[key] = arg_dict[key]

  return options

This will load up all the default option. Any options put on the command line will override or add to the options dict.

answered Apr 17, 2015 at 12:44

manicphase

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Comments

Community · Accepted Answer · 2017-05-23 10:10:17Z

First of all, I'd move code into a main section so that you can import config_parser_details without executing code:

if __name__ == '__main__':
    main()

def main():
    Config = ConfigParser.ConfigParser()
    Config.read("system.config")
    filename = "system.config"

    company = ConfigSectionMap("company")['companyname']
    name = ConfigSectionMap("profile")['name']
    joindate = ConfigSectionMap("profile")['joining']

Secondly, I'd use STB land's suggestion of parsing the command line with argparse, something like:

def main():
    # do the parsing thing first, then:
    filename = args.filename
    do_stuff(filename)

This way you can neatly use python's own unit test framework or nosetests to write test file that don't require you to manually specify parameters:

def test_basic():
    # create a temporary file with tempfile.NamedTemporaryFile
    tmpfile = tempfile.NamedTemporaryFile()
    # add test data to tmpfile
    do_stuff(tmpfile)

    # check the output
    assert ....

This comes with the added benefit of not having global variables, which will complicate your life later.

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