configuration - Python Config Parser (Duplicate Key Support)

Question

So I recently started writing a config parser for a Python project I'm working on. I initially avoided configparser and configobj, because I wanted to support a config file like so:

key=value
key2=anothervalue

food=burger
food=hotdog
food=cake icecream

In short, this config file is going to be edited via the command line over SSH often. So I don't want to tab or finicky about spacing (like YAML), but I also want avoid keys with multiple values (easily 10 or more) being line wrapped in vi. This is why I would like to support duplicate keys.

An my ideal world, when I ask the Python config object for food, it would give me a list back with ['burger', 'hotdog', 'cake', 'icecream']. If there wasn't a food value defined, it would look in a defaults config file and give me that/those values.

I have already implemented the above

However, my troubles started when I realized I wanted to support preserving inline comments and such. The way I handle reading and writing to the config files, is decoding the file into a dict in memory, read the values from the dict, or write values to the dict, and then dump that dict back out into a file. This isn't really nice for preserving line order and commenting and such and it's bugging the crap out of me.

A) ConfigObj looks like it has everything I need except support duplicate keys. Instead it wants me to make a list is going to be a pain to edit manually in vi over ssh due to line wrapping. Can I make configobj more ssh/vi friendly?

B) Is my homebrew solution wrong? Is there a better way of reading/writing/storing my config values? Is there any easy way to handle changing a key value in a config file by just modifying that line and rewriting the entire config file from memory?

Answer 1

Well I would certainly try to leverage what is in the standard library if I could.

The signature for the config parser classes look like this:

class ConfigParser.SafeConfigParser([defaults[, dict_type[, allow_no_value]]])

Notice the dict_type argument. When provided, this will be used to construct the dictionary objects for the list of sections, for the options within a section, and for the default values. It defaults to collections.OrderedDict. Perhaps you could pass something in there to get your desired multiple-key behavior, and then reap all the advantages of ConfigParser. You might have to write your own class to do this, or you could possibly find one written for you on PyPi or in the ActiveState recipes. Try looking for a bag or multiset class.

I'd either go that route or just suck it up and make a list:

foo = value1, value2, value3