Strings and numbers¶

Unchanged values keep their spelling: quotes, 1_000, +12, and 0xFF survive a load and save. These examples show how to control values you edit or create.

Keep quotes when editing¶

Set preserve_quotes = True before loading, then use replace() to edit a quoted string while keeping its style:

from yamluna import YAML

yaml = YAML()
yaml.preserve_quotes = True
config = yaml.load('image: "app:1.4"\n')
config['image'] = config['image'].replace('1.4', '1.5')
print(yaml.dump(config), end='')

Output:

image: "app:1.5"

For a new value, use DoubleQuotedScalarString('text') or SingleQuotedScalarString('text') with the same setting enabled.

Write multiline text¶

LiteralScalarString writes a | block that keeps line breaks:

from yamluna import YAML, LiteralScalarString

yaml = YAML()
config = {'script': LiteralScalarString('echo hello\necho done\n')}
print(yaml.dump(config), end='')

Output:

script: |
  echo hello
  echo done

Use FoldedScalarString for a > block whose lines read as a paragraph. walk_tree(config) converts all strings containing newlines into literal blocks.

Keep number formatting¶

Use in-place arithmetic, such as +=, to keep a loaded number's format:

from yamluna import YAML

yaml = YAML()
config = yaml.load('mask: 0x0f\ncount: 1_000\n')
config['mask'] += 1
config['count'] += 1
print(yaml.dump(config), end='')

Output:

mask: 0x10
count: 1_001

Ordinary arithmetic, such as config['mask'] = config['mask'] + 1, returns a plain integer and writes 16.

YAML versions¶

yamluna uses YAML 1.2 by default: yes, no, on, and off are strings; true and false are booleans. A document beginning with %YAML 1.1 and --- uses the older rules, where yes and on are also booleans and 0755 is the octal number 493 rather than the decimal 755.

Scalar type reference lists the available formatting classes.