PyYAML
The most commonly used YAML parsing and generation library in the Python ecosystem, supporting multiple YAML versions.
Timeline (last 90 days)
The YAML specification requires keys in a mapping to be unique, but does not mandate that parsers raise an error on duplicate keys; mainstream implementations such as PyYAML default to a 'last one wins' strategy, keeping the final value without producing a warning.
Python's PyYAML long defaulted to YAML 1.1, Go's go-yaml v2 is also 1.1, and only v3 switched to 1.2 semantics.
All Facts (2)
The YAML specification requires keys in a mapping to be unique, but does not mandate that parsers raise an error on duplicate keys; mainstream implementations such as PyYAML default to a 'last one wins' strategy, keeping the final value without producing a warning.
50%UnverifiedPython's PyYAML long defaulted to YAML 1.1, Go's go-yaml v2 is also 1.1, and only v3 switched to 1.2 semantics.
50%