Errors

The exception hierarchy mirrors PyYAML: every error raised by the package derives from YAMLError, so except yaml.YAMLError catches all of them. Parser-side errors carry a source position; the remaining errors describe path, style, alias, and emission failures.

Hierarchy

YAMLError
├── MarkedYAMLError
│   ├── ScannerError
│   ├── ParserError
│   ├── ComposerError
│   └── ConstructorError
├── EmitterError
├── RepresenterError
├── SerializerError
├── PathError
├── StyleError
└── AliasError

MarkedYAMLError

Base class for errors that carry a source position from the Rust parser. Its str() is a multi-line message ending in a mark such as in "unicode string", line 1, column 7.

• context – description of what was being parsed, or None.
• context_mark – position where the enclosing construct started.
• problem – the actual problem description.
• problem_mark – position where the problem was detected.
• note – additional explanation, or None.

ScannerError

Lexing failed: a quote or bracket is unterminated, a character is not valid in the current context, or indentation is malformed.

ParserError

The token stream does not form valid YAML grammar, for example a flow sequence that is never closed. The parser also enforces a 128-level nesting depth limit (matching libyaml's default): input nested deeper than that raises ParserError instead of exhausting the stack.

ComposerError

The document structure is invalid before construction: an alias *name references no defined anchor, or the input holds more than one document where a single document was expected.

ConstructorError

A value could not be constructed. Raised for duplicate mapping keys and, in the safe engine, for non-standard application tags such as !!python/object/apply:....

EmitterError

The native emitter failed while writing YAML text.

RepresenterError

A value cannot be represented. Raised by the safe engine when Tagged values or custom application tags appear in safe_dump() input, and when a value such as a complex number is dumped in a place where no YAML representation exists.

SerializerError

The serialization step failed before emission, for example when a mapping key cannot be represented: complex numbers are supported as values but raise SerializerError when used as mapping keys.

PathError

A path does not exist. Raised by document[key] for missing paths, and by assignments below a scalar node.

>>> yaml.load("a: 1\n")["missing"]
Traceback (most recent call last):
    ...
PathError: no YAML node at path ('missing',)

StyleError

A style request does not fit the value or the request is malformed: a non-string value with single/double/literal/folded style, chomping or a block indentation indicator on a non-block scalar, a comment line without #, a tag not starting with !, an invalid anchor name, or an inline comment spanning several lines.

AliasError

An alias operation is impossible: removing a node that still has aliases, removing an anchor still referenced by aliases, or aliasing across two documents.