MergedView Class

MergedView Class¶

The MergedView class provides a read-only view of a YamlDocument with merge keys (<<: *anchor) resolved. It is accessed via doc.merged().

Overview¶

class MergedView(Mapping):
    """Read-only view of a YAML document with merge keys resolved."""

The view is built lazily from YamlDocument.to_dict(), which resolves anchors and merge keys during serialization. The original AST is never mutated.

Constructor¶

MergedView.__init__()¶

MergedView.__init__(document: YamlDocument) -> None

Parameters:

• document — A YamlDocument instance

If the document root is a sequence, the view converts it to an integer-keyed mapping ({0: item0, 1: item1, ...}).

Methods¶

__getitem__()¶

Access a value by key.

__getitem__(key: str | int) -> Any

Child dicts and lists are wrapped recursively in MergedView._DictView and MergedView._ListView respectively.

Example:

doc = pyrs_yaml.parse("""
defaults: &defaults
  timeout: 30
  retries: 3

config:
  <<: *defaults
  timeout: 60
""")

view = doc.merged()
print(view["config"]["timeout"])  # 60 (overrides merged value)
print(view["config"]["retries"])  # 3 (inherited from merge)

__len__()¶

Return the number of top-level items.

__len__() -> int

__iter__()¶

Iterate over top-level keys.

__iter__() -> Iterator[str | int]

__repr__()¶

__repr__() -> str

Returns MergedView({...}) with the internal dict representation.

get()¶

get() is inherited from collections.abc.Mapping — it provides get(key, default=None).

get(key: str | int, default: Any = None) -> Any

Merge Key Resolution¶

Keys are resolved with the following precedence (highest wins):

1. Keys defined directly in the merging document
2. Keys from merged anchors (in the order they appear in <<:)
3. Later anchors override earlier ones

Root Type Support¶

Example¶

import pyrs_yaml

doc = pyrs_yaml.parse("""
base: &base
  host: localhost
  port: 8080

prod:
  <<: *base
  host: prod.example.com
  debug: false
""")

merged = doc.merged()
assert merged["base"]["host"] == "localhost"
assert merged["prod"]["host"] == "prod.example.com"  # overridden
assert merged["prod"]["port"] == 8080  # inherited
assert merged["prod"]["debug"] is False  # own key