Automatically read configuration values in Python

Question

I would like to read a configuration file in Python completely into a data structure without explicitly 'getting' each value. The reason for doing so is that I intend to modify these values programatically (for instance, I'll have a variable that says I want to modify [Foo] Bar = 1 to be [Foo] Bar = 2), with the intention of writing a new configuration file based on my changes.

At present, I'm reading all the values by hand:

parser = SafeConfigParser()
parser.read(cfgFile)
foo_bar1 = int(parser.get('Foo', 'Bar1'))
foo_bar2 = int(parser.get('Foo', 'Bar2'))

What I would love to have (didn't find much Google-wise) is a method to read them into a list, have them be identified easily so that I can pull that value out of the list and change it.

Essentially referencing it as (or similarly to):

config_values = parser.read(cfgFile)
foo_bar1      = config_values('Foo.bar1')

Could you just overload __getitem__ (or __call__) on a class that wraps the config parser? Then, when you do class['Foo.Bar1] (or class('Foo.Bar1')) you can split on the period and look it up in the config_parser object? It seems that what you want to do is very close to what the parser already does. — Sam Mussmann
– Sam Mussmann, Commented Nov 9, 2012 at 14:36
@SamMussmann -- It looks like we were thinking the same thing. — mgilson
– mgilson, Commented Nov 9, 2012 at 14:36

mgilson · Accepted Answer · 2012-11-09 14:35:55Z

3

Sorry if I'm misunderstanding -- This really doesn't seem much different than what you have -- It seems like a very simple subclass would work:

class MyParser(SafeConfigParser):
    def __call__(self,path,type=int):
        return type(self.get(*path.split('.')))

and of course, you wouldn't actually need a subclass either. You could just put the stuff in __call__ into a separate function ...

answered Nov 9, 2012 at 14:35

mgilson

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1 Comment

erik Over a year ago

This looks interesting, but I'm slightly confused. Is this overloading the parser.read function? I'd like to just read all the config values into a list and then pull them out dictionary style (similar to @Ryan G's answer in a way)

jfs · Accepted Answer · 2012-11-09 16:22:15Z

2

import sys
from ConfigParser import SafeConfigParser

parser = SafeConfigParser()
parser.readfp(sys.stdin)

config = dict((section, dict((option, parser.get(section, option))
                             for option in parser.options(section)))
              for section in parser.sections())
print config

Input

[a]
b = 1
c = 2
[d]
e = 3

Output

{'a': {'c': '2', 'b': '1'}, 'd': {'e': '3'}}

answered Nov 9, 2012 at 16:22

jfs

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Comments

Ryan G · Accepted Answer · 2012-11-09 15:02:24Z

2

Are you running python 2.7?

There's a nifty way, I discovered a few months back, to parse the config file and setup a dictionary using dictionary comprehension.

config = ConfigParser.ConfigParser()
config.read('config.cfg')
# Create a dictionary of complete config file, {'section':{'option':'values'}, ...}
configDict = {section:{option:config.get(section,option) for option in config.options(section)} for section in config.sections()}

Although this way is harder to read, it take's up less space, and you don't have to explicitly state every variable that you want to get.

Note: This won't work on python 2.6 (*that I know of). I've written scripts in the past where I used this, and since I'm running 2.7 on Windows, somebody on a linux machine, running 2.6, will crash on the dictionary comprehension.

--Edit--

You will need to still manually change the data types of the values.

answered Nov 9, 2012 at 15:02

Ryan G

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6 Comments

erik Over a year ago

That would be lovely...but yea I'm running 2.6 (had 2.7 tag on by mistake)

jfs Over a year ago

@espais: you could use it on Python 2.6 if you replace {k: v for ..} with dict((k, v) for ..)

erik Over a year ago

@J.F.Sebastian: Am I missing something?

cfg_dict = dict(section: dict(option:cfg.get(section,option) for option in cfg.options(section)) for section in cfg.sections())

throws an error on the 2nd param after cfg.options(section))

jfs Over a year ago

@espais: yes. Replace a: b with (a, b)

erik Over a year ago

@J.F.Sebastian: sorry for my lack of Python-knowledge....but now I see this: SyntaxError: Generator expression must be parenthesized if not sole argument...I tried parenthesizing the 2nd argument but that didn't help

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