pyyaml-core - YAML 1.2 Core Schema Support for PyYAML

This module can be used on top of PyYAML to load YAML 1.2 files. It depends on PyYAML and inherits from it, it's not a fork.

Currently it supports enabling all YAML 1.2 Core Schema tags on top of the PyYAML BaseLoader. It does not (yet) support other tags like the << merge key. You can add custom constructors, though.

For more information see the comparison of 1.1 and 1.2 schemas.

Examples

import yaml
from yamlcore import CoreLoader
from yamlcore import CoreDumper

y = """
---
1.1: # strings
- yes
- no # norway problem anymore
- 1__0
- 10:20
- +0b100
- 0x4_2

core:
- true
- 0o10
- 0x42
- ~
- .inf
"""

d = yaml.load(y, Loader=CoreLoader)
out = yaml.dump(d, Dumper=CoreDumper)

You can also use CCoreLoader and CCoreDumper for using the libyaml based parser and emitter.

Why?

At the time of this writing, there is a pending pull request that adds YAML 1.2 Core Schema Support for PyYAML.

It's blocked because there is a plan to redesign the API, and no new things shall be added using the old API at this point.

So as long as PyYAML doesn't merge this, you can use this module as an alternative.

Differences

There are other differences in behaviour to PyYAML.

Duplicate keys are not allowed

The YAML spec forbids duplicate keys. PyYAML allows them, which leads to accidentally added duplicate keys in YAML files, eventually.

I can't see a good use case that people would want to allow duplicate keys in a typical YAML loading process. For the use cases I see you would want your own constructor anyway.

If this is breaking anyone's use case, please let me know.