How to write a parser for a configuration file in python

Question

I have a non-standard configuration file, for which I want to write a python parser.

What is the best approach to writing a parser from scratch?

Example of a configuration file:

// Comment 
conf OPTION_NAME {
     (
       ( option1:"string"
         option2:"14"
       )
     )
}


// Comment2 
conf OPTION_NAME2 {
     (
       ( option1:"string2"
         option2:"15"
       )
     )
}

Unfortunately, no , it's a legacy file, not under my control. But this is a good exercise for any non-standard conf file/code. — HerbSpiral, Feb 27 '12 at 15:29
There's not enough information here. What is the grammar of this language? — David Heffernan, Feb 27 '12 at 15:31
Write a BNF grammar first, (if you can't change the config so you can). Perhaps this SO post might help. http://stackoverflow.com/questions/264262/grammar-writing-tools — Tony Hopkinson, Feb 27 '12 at 15:32
I would say that this really depends on how flexible your format is. For instance, I don't see the point of the double nesting inside your options unless it allows for constructions you didn't tell us of. — jena, Feb 27 '12 at 15:33
I've used [`PyParsing`](http://pyparsing.wikispaces.com/) the few times I've had to write a parser in Python. The first thing you should do is write down the grammar of your language. — Katriel, Feb 27 '12 at 15:48

score 2 · Answer 1 · answered Feb 27 '12 at 15:32

I would personally use PLY: http://www.dabeaz.com/ply/

Here's a simple example:

http://www.dabeaz.com/ply/example.html

Here's an example from one of my own projects:

https://github.com/fogleman/FeedNotifier/blob/master/filters.py

Alternatively, since the files look very simple, I might just use a handmade Finite State Machine to do the parsing.

How to write a parser for a configuration file in python

1 Answers1