YAML may be the most human friendly format for structured data invented so far.
YAML examples and usage in notable Python apps
YAML is a feature-overcrept language. Most packages below use its subset.
Full YAML parsers
PyYAML - http://pyyaml.org/ - due to complexity of YAML spec, this is the only package that tried to be compliant. It is C-based.
Parsers for YAML subsets
Luckily, you may not need the full YAML spec. These libraries can parse only the sweetest parts of YAML spec that you may reuse in your configs.
Unfortunately, there doesn't seem to be any Python code that parses YAML subset - pretty much every lib uses PyYAML. But still it worth to list honorable mentions that may be modified to build mininal parsers: