ruamel.yaml behavior differences¶

These are the main changes to expect when switching from ruamel.yaml 0.19.1 to yamluna 0.1.0. Start with the migration guide for code changes.

Saved files look closer to the input¶

yamluna keeps each loaded collection's indentation, unused anchors, document markers, and original number spelling. For example:

from yamluna import YAML

source = '---\ncount: +12\nports:\n  - 80\n...\n'
yaml = YAML()
print(yaml.dump(yaml.load(source)), end='')

Output:

---
count: +12
ports:
  - 80
...

With ruamel.yaml's default YAML(), this example saves without --- and ..., with count: 12, and with the list dash at column one. yamluna keeps all four details without extra settings.

Changes that can affect your code¶

Area	yamluna behavior
Comments	Move with reordered entries; attached comments are removed with deleted entries
Key renaming	`mapping.rename(old, new)` keeps position and comments
Class registration	Per `YAML()` instance; class sources are written using `%TAG`
Ambiguous tags	Raise an error instead of choosing a class by registration order
Quoting	Unchanged quotes survive by default; enable `preserve_quotes` for quoted-string edits and new quoted values
Allowed duplicate keys	Warn and keep the last value
Document markers	`None` keeps them; `True` adds them; `False` removes them
Multiple documents	`load_all()` returns a list rather than a generator
Source positions	An unavailable `.lc` position returns `None`

Comment movement still has exceptions around first items and list insertions. Read known limitations and check files affected by those operations.

For side-by-side output and the corpus results, see the comparison.