Question

I read the part of the docs and saw that the ConfigParser returns a list of key/value pairs for the options within a section. I figured that keys did not need to be unique within a section, otherwise the parser would just return a mapping. I designed my config file schema around this assumption, then sadly realized that this is not the case:

>>> from ConfigParser import ConfigParser >>> from StringIO import StringIO >>> fh = StringIO(''' ... [Some Section] ... spam: eggs ... spam: ham ... ''') >>> parser = ConfigParser() >>> parser.readfp(fh) >>> print parser.items('Some Section') [('spam', 'ham')] 

Then I went back and found the part of the docs that I should have read:

Sections are normally stored in a builtin dictionary. An alternative dictionary type can be passed to the ConfigParser constructor. For example, if a dictionary type is passed that sorts its keys, the sections will be sorted on write-back, as will be the keys within each section.

To keep my existing configuration file scheme (which I really like now 😉 I’m thinking of passing a mapping-like object as mentioned above that accumulates values instead of clobbering them. Is there a simpler way to prevent key/value collapse that I’m missing? Instead of making a crazy adapter (that could break if ConfigParser‘s implementation changes) should I just write a variant of the ConfigParser itself?

I feel like this may be one of those ‘duh’ moments where I’m only seeing the difficult solutions.

[Edit:] Here’s a more precise example of how I’d like to use the same key multiple times:

[Ignored Paths] ignore-extension: .swp ignore-filename: tags ignore-directory: bin 

I dislike the comma-delimited-list syntax because it’s hard on the eyes when you scale it to many values; for example, a comma delimited list of fifty extensions would not be particularly readable.

Answer 1

ConfigParser isn’t designed to handle such conditions. Furthermore, your config file doesn’t make sense to me.

ConfigParser gives you a dict-like structure for each section, so when you call parser.items(section), I’m expecting similar output to dict.items(), which is just a list of key/value tuples. I would never expect to see something like:

[('spam', 'eggs'), ('spam', 'ham')] 

Not to mention, how would you expect the following to behave?:

parser.get('Some Section', 'spam') 

Which is the intended way to retrieve values.

If you want to store multiple values for the same key, I would suggest something like this in your config file:

[Some Section] spam: eggs, ham 

And this in your code:

spam_values = [v.strip() for v in parser.get('Some Section', 'spam').split(',')] 

Of course, this will only work for values that don’t contain commas themselves or handle quoting. For that, you should employ a more advanced technique (see this and this).

EDIT: If you don’t mind the extra dependency, You could check out ConfigObj, which natively supports lists as a value type.