Handle errors¶

Catch YAMLError when you want to report a YAML problem to the user. Errors with a source position provide problem_mark.

Report the line and column¶

from yamluna import YAML, YAMLError

yaml = YAML()
try:
    yaml.load('replicas: 2\nreplicas: 5\n')
except YAMLError as error:
    print(type(error).__name__)
    mark = getattr(error, 'problem_mark', None)
    if mark is not None:
        print(f'Line {mark.line + 1}, column {mark.column + 1}')

Output:

DuplicateKeyError
Line 2, column 1

print(error) includes the explanation and available location details. The stored line and column numbers start at zero; add one for display.

Common problems¶

Error	What to do
`ScannerError`	Fix the YAML syntax or undefined alias at the reported location
`DuplicateKeyError`	Remove or rename the repeated key
`ComposerError`	Use `load_all()` for a stream containing multiple documents
`ConstructorError`	Check the tag registration or your `from_yaml` hook
`RepresenterError`	Convert the value to a supported type or register its class
`YAMLStreamError`	Pass YAML text, a `Path`, or an appropriate file object

File errors such as FileNotFoundError and PermissionError are ordinary Python exceptions. Catch OSError separately when reporting file-access problems.

Duplicate keys¶

By default, repeated keys are errors. If you deliberately accept them, set yaml.allow_duplicate_keys = True: yamluna warns and keeps the last value. Saving writes one entry for that key. A repeated << merge key always raises.

See the error reference for the exception classes.