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How to parse configuration files in Python

There are several solutions to parse configuration files in Python.

These are usually text files contain a list of options with a name and a value, such as "port=8080" or "user: admin". More elaborate configuration files such as "INI files" on Windows contain sections to organize options. A section starts with a name between square brackets, such as "[section1]".

ConfigParser for INI files with sections

See http://docs.python.org/library/configparser.html

This parser is powerful, but it does not support simple configuration files without sections.

SimpleConfigParser for config files without sections

As Fredrik Lundh proposed on the python-dev mailing-list, it is quite simple to extend ConfigParser to support files without sections: http://mail.python.org/pipermail/python-dev/2002-November/029987.html

I have made a module called SimpleConfigParser based on that idea, that you can reuse in your own projects. See attached file below.

Sample usage:

import SimpleConfigParser
filename = 'sample_config_no_section.ini'
cp = SimpleConfigParser.SimpleConfigParser()
cp.read(filename)
print 'getoptionslist():', cp.getoptionslist()
for option in cp.getoptionslist():
    print "getoption('%s') = '%s'" % (option, cp.getoption(option))
print "hasoption('wrongname') =", cp.hasoption('wrongname')

 

ConfigObj for more advanced config files

ConfigObj is able to handle INI config files with sections and subsections, among other enhancements.

see http://www.voidspace.org.uk/python/configobj.html

ElementTree for XML config files

see http://www.decalage.info/en/python/etree

Custom config file parser

In fact it is very easy to create your own configuration file parser, thanks to Python string methods such as split() and strip(). For example the following function is able to parse simple configurations files and return a dictionary of parameters:

COMMENT_CHAR = '#'
OPTION_CHAR =  '='
 
def parse_config(filename):
    options = {}
    f = open(filename)
    for line in f:
        # First, remove comments:
        if COMMENT_CHAR in line:
            # split on comment char, keep only the part before
            line, comment = line.split(COMMENT_CHAR, 1)
        # Second, find lines with an option=value:
        if OPTION_CHAR in line:
            # split on option char:
            option, value = line.split(OPTION_CHAR, 1)
            # strip spaces:
            option = option.strip()
            value = value.strip()
            # store in dictionary:
            options[option] = value
    f.close()
    return options
 
options = parse_config('config.ini')
print options

 

 

AttachmentSize
SimpleConfigParser-0.02.zip2.01 KB

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Sat, 02/25/2012 - 22:57 — trinar (not verified)

Improved custom config parser

Hi, here is a code of my ini files parser in python.
I made it so it can accept comment that starts with '#' or ';' and they end on the line break so can start after the section or key-value pairs.

#comment1
;comment2

The key-value separator can be '=' or ':' and the whitespaces can be arbitrary.
key1: value1
key2 = value2

There can be key-value pairs before the first section, they are stored in the 'global' section then.
And the sections can be nested with dot separation.
[section.subsection.subsubsection]

Here is the code:

  1. class ParseINI(dict):
  2.   def __init__(self, f):
  3.     self.f = f
  4.     self.__read()
  5.  
  6.   def __read(self):
  7.     with open(self.f, 'r') as f:
  8.       slovnik = self
  9.       for line in f:
  10.         if not line.startswith("#") and not line.startswith(';') and line.strip() != "":
  11.           line = line.replace('=', ':')
  12.           line = line.replace(';', '#')
  13.           index = line.find('#')
  14.           line = line[:index]
  15.           line = line.strip()
  16.           if line.startswith("["):
  17.             sections = line[1:-1].split('.')
  18.             slovnik = self
  19.             for section in sections:
  20.               if section not in slovnik:
  21.                 slovnik[section] = {}
  22.               slovnik = slovnik[section]
  23.           else:
  24.             if not self:
  25.               slovnik['global'] = {}
  26.               slovnik = slovnik['global']
  27.             parts = line.split(":", 1)
  28.             slovnik[parts[0].strip()] = parts[1].strip()
  29.  
  30.   def items(self, section):
  31.     try:
  32.       return self[section]
  33.     except KeyError:
  34.       return []

The use is simple:

ini = ParseINI('path/to/file.ini')
value = ini['section']['subsection']['key']