Keep ConfigParser output files sorted

Question

I've noticed with my source control that the content of the output files generated with ConfigParser is never in the same order. Sometimes sections will change place or options inside sections even without any modifications to the values.

Is there a way to keep things sorted in the configuration file so that I don't have to commit trivial changes every time I launch my application?

Answer 1

Looks like this was fixed in Python 3.1 and 2.7 with the introduction of ordered dictionaries:

The standard library now supports use of ordered dictionaries in several modules. The configparser module uses them by default. This lets configuration files be read, modified, and then written back in their original order.

Answer 2

No. The ConfigParser library writes things out in dictionary hash order. (You can see this if you look at the source code.) There are replacements for this module that do a better job.

I will see if I can find one and add it here.

http://www.voidspace.org.uk/python/configobj.html#introduction is the one I was thinking of. It's not a drop-in replacement, but it is very easy to use.

Answer 3

If you want to take it a step further than Alexander Ljungberg's answer and also sort the sections and the contents of the sections you can use the following:

config = ConfigParser.ConfigParser({}, collections.OrderedDict)
config.read('testfile.ini')
# Order the content of each section alphabetically
for section in config._sections:
    config._sections[section] = collections.OrderedDict(sorted(config._sections[section].items(), key=lambda t: t[0]))

# Order all sections alphabetically
config._sections = collections.OrderedDict(sorted(config._sections.items(), key=lambda t: t[0] ))

# Write ini file to standard output
config.write(sys.stdout)

This uses OrderdDict dictionaries (to keep ordering) and sorts the read ini file from outside ConfigParser by overwriting the internal _sections dictionary.

Answer 4

ConfigParser is based on the ini file format, who in it's design is supposed to NOT be sensitive to order. If your config file format is sensitive to order, you can't use ConfigParser. It may also confuse people if you have an ini-type format that is sensitive to the order of the statements...