As noted here, I should add an extra so you can do pip install python-frontmatter[toml] (or [tomli]) and get everything in one shot.

I would recommend rtoml

See: https://github.com/pwwang/toml-bench

FYI Python is gaining tomllib in the 3.11 standard library, which is adapted from tomli

FYI Python is gaining tomllib in the 3.11 standard library, which is adapted from tomli

tomli is also a good choice, not only because of the reason you mentioned, it's implemented in pure python. If we don't need .load() or .loads(), which is implemented in a different package (tomli_w), then I am not against tomli here.

With Python 3.11 now available this feels like a higher priority. Since tomllib is read-only, I need to think about how to include it. Some options, in no particular order:

1. Use tomllib but make the TOMLHandler read-only by default. In that case, you could read TOML but would have to write in another format, unless you install another library (probably tomli_w).
2. Add tomli_w as a dependency. That preserves current functionality, maybe extends it a bit, but adds a dependency.
3. Require tomli_w to use TOMLHandler. Again, basically the same as now, but with a different optional dependency.
4. Use tomlkit to get reading and writing and also preserve format.

I don't use TOML enough to have a strong opinion here. Would like to hear from people who use the current TOML support.

My suggestion: Add tomli_w as a dependency, and tomli as a dependency for when Python version is < 3.11

Something like this:

install_requires = 
  tomli==1.2.3; python_version < 3.11
  tomli-w==1.2.3

And in your Python code:

import tomli_w
if sys.version_info() >= (3, 11):
    import tomllib as tomli
else:
    import tomli