Either/or schema validation of different, equally valid different kinds of YAML

StrictYAML can be directed to parse two different elements or blocks of YAML.

If the first thing does not parse correctly, it attempts to parse the second. If the second does not parse correctly, it raises an exception.

from strictyaml import Map, Bool, Int, Str, YAMLValidationError, load
from ensure import Ensure

schema = Str() | Map({"a": Bool() | Int()})

Boolean first choice true:

a: yes
Ensure(load(yaml_snippet, schema)).equals({"a": True})

Boolean first choice false:

a: no
Ensure(load(yaml_snippet, schema)).equals({"a": False})

Int second choice:

a: 5
Ensure(load(yaml_snippet, schema)).equals({"a": 5})

Invalid not bool or int:

a: A
load(yaml_snippet, schema)
strictyaml.exceptions.YAMLValidationError:
when expecting an integer
found arbitrary text
  in "<unicode string>", line 1, column 1:
    a: A
     ^ (line: 1)

Change item after validated:

a: yes
yaml = load(yaml_snippet, schema)
yaml['a'] = 5
assert yaml['a'] == 5

Executable specification

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